A waterborne matte antibacterial light absorbing coating and a method of making the same

Abstract

This invention relates to the field of fine chemical materials and special water-based industrial coatings manufacturing technology, specifically to a water-based matte antibacterial light-absorbing coating and its preparation method. The invention discloses a water-based matte antibacterial light-absorbing coating and its preparation method. The coating comprises liquid A and liquid B. Liquid A contains a self-matting water-based hydroxyl polyurethane dispersion, dual-particle-size textured powder, swellable polymer microspheres, and an antibacterial agent, while liquid B contains a water-based isocyanate curing agent. This invention achieves a unified ultra-low gloss and high blackness (60° gloss <0.2GU, L value <15) by constructing a four-level light trap structure of self-matting resin, dual-particle-size textured powder, and swellable microspheres forming a contracted interfacial cavity. The reverse particle size distribution and in-situ swelling process ensure that the microspheres accurately fill the gaps between fillers. Combined with the interfacial cavity slow-release effect, the antibacterial rate of the coating reaches over 99%.

Description

Technical Field

[0001] This invention relates to the field of fine chemical materials and special water-based industrial coatings manufacturing technology, specifically to a water-based matte antibacterial light-absorbing coating and its preparation method. Background Technology

[0002] In traditional polymer coating science and engineering applications, there is an inherent physical contradiction between matte finish and high blackness. Traditional coating matte finish technology mainly relies on adding a large amount of externally added irregular matting powder to the system. The principle is that these matting powders protrude significantly from the resin surface during coating curing and shrinkage, creating microscopic surface roughness. When light shines on the coating, the original specular reflection is converted into diffuse reflection in all directions, resulting in extremely low gloss values ​​recorded at the angle of light received by a gloss meter. However, this diffuse reflection mechanism based on Mie scattering and Rayleigh scattering inevitably leads to a large amount of light being scattered back into the air or into the observer's field of vision. At the visual and optical sensor end, this strong scattering effect manifests as severe whitening, graying, and fogging of the coating, completely destroying the depth of the black coating, causing a significant increase in the blackness L value and a precipitous drop in light absorption efficiency.

[0003] To avoid the whitening defects caused by the addition of silicone-based matting agents, the coatings and resins industry has recently shifted its research focus to self-matting resin systems. For example, CN117844356A discloses a water-based two-component matte anti-scratch topcoat, its preparation method, and its application. The prepared water-based two-component matte anti-scratch topcoat includes component A and component B. Component A comprises the following raw materials in the following mass fractions: 45%~75% hydroxyl acrylic emulsion; 0.01%~2.2% acrylic copolymer matting agent; 0.01%~2% hydroxyl-modified polysiloxane emulsion; 2.55%~5% additives; and water as the balance. Component B includes an isocyanate curing agent. The mass ratio of component A to component B is 100:(5~10). Further, by adding 0.01%~... A 10% waterborne self-matting resin can enable the waterborne two-component matte anti-scratch topcoat to achieve a fully matte finish. CN113736353A discloses a waterborne abrasion-resistant and chemical-resistant matte coating suitable for automotive interiors, its preparation, and application. This waterborne abrasion-resistant and chemical-resistant matte coating comprises: 60-70 parts of component A, 20-25 parts of component B, and 5-20 parts of component C. Component A includes: polyhydroxy acrylic resin, polyurethane resin, defoamer, wetting and leveling agent, color paste, silica matting powder, abrasion-resistant filler, thickener, amine neutralizer, co-solvent, and deionized water; component B includes HDI curing agent and solvent; and component C is deionized water. However, relying solely on the intrinsic microphase separation of the self-matting resin presents a theoretical physical bottleneck in its lower extinction limit. When facing the extreme optical requirements of blackbody-level total absorption, the limited roughness of the macromolecular phase alone is insufficient, and photons still have a high probability of shallow reflection and escape.

[0004] In summary, how to break down the mutually exclusive barrier between matte and blackness from the dual dimensions of underlying material design and preparation process, and construct a light trap with abyss-level ultra-low gloss and high blackness light absorption performance, while also taking into account the long-lasting slow-release function of antibacterial agents, has become an urgent technical problem to be solved. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a water-based matte antibacterial light-absorbing coating and its preparation method, so as to solve the inherent contradiction between matte finish and blackness and the insufficient antibacterial durability in the prior art.

[0006] The specific technical solution is as follows:

[0007] A water-based matte antibacterial light-absorbing coating and its preparation method are disclosed. The light-absorbing coating comprises liquid A and liquid B. Liquid A comprises the following components in parts by weight: 45-65 parts of self-matte water-based hydroxyl polymer dispersion, 0.5-1.5 parts of polyether-modified styrene-maleic anhydride copolymer dispersant, 0.4-0.8 parts of polyether siloxane copolymer substrate wetting agent, 5-10 parts of carbon black-based water-based color paste, 15-25 parts of water-based filler, and 2-4 parts of cross-linked polyacrylic acid-acrylate copolymer swellable. Microspheres, 3-5 parts texture powder A, 3-5 parts texture powder B, 4-6 parts matte powder, 1-3 parts antibacterial agent, 0.2-0.6 parts polyether siloxane copolymer defoamer containing fumed silica, 1-3 parts hydrophobic modified alkali swelling thickener, and 5-12 parts deionized water; wherein liquid B comprises the following components by weight: 90-100 parts water-based isocyanate curing agent, 0.4-0.8 parts molecular sieve dehydrating agent, 4-8 parts film-forming aid, and 0.2-0.4 parts fumed silica anti-settling agent.

[0008] Furthermore, the weight ratio of liquid A and liquid B ranges from 6:1 to 8:1.

[0009] Furthermore, the cross-linked polyacrylic acid-acrylate copolymer swellable microspheres have a dry particle size of 2~8μm, and after swelling in solution A, the particle size is 8~12μm, and the swelled particle size is smaller than the particle size of the textured powder A.

[0010] Furthermore, the textured powder A has a particle size of 15~25μm; the textured powder B has a particle size of 100~160μm.

[0011] Furthermore, the self-matting waterborne hydroxyl polymer dispersion is selected from one of self-matting waterborne hydroxyl polyurethane dispersion or self-matting waterborne hydroxyl acrylic dispersion, and its hydroxyl value is 60~80mgKOH / g; the waterborne isocyanate curing agent has an isocyanate group content of 16%~18%.

[0012] Furthermore, the antibacterial agent is one of silver-loaded zeolite molecular sieve or nano zinc oxide; the film-forming aid is selected from a compound mixture of propylene glycol methyl ether acetate and propylene glycol diacetate or dipropylene glycol butyl ether.

[0013] A water-based matte antibacterial light-absorbing coating and its preparation method include the following steps:

[0014] S1: In a high-speed dispersion tank, add the self-degrading waterborne hydroxyl polymer dispersion, polyether modified styrene-maleic anhydride copolymer dispersant, polyether siloxane copolymer substrate wetting agent, carbon black-based waterborne color paste, and waterborne filler slurry in sequence. Start stirring for premixing, and then increase the speed for high-speed dispersion to ensure that all components are fully mixed and uniform, thus obtaining a high-solids content base material.

[0015] S2: Reduce the stirring speed and slowly add dry cross-linked polyacrylic acid-acrylate copolymer swellable microspheres, texture powder A, texture powder B, and matte powder. Stir at low speed to fully mix the microspheres, powders, and high solids content matrix. The system contains no free water, and the microspheres remain dry without any premature swelling. Then, increase the stirring speed for high-speed dispersion to obtain a dry dispersion slurry. Next, adjust the stirring speed and slowly add deionized water to the slurry through a peristaltic pump. The swellable microspheres absorb water and swell uniformly in situ within the confined gaps of the filler. After the addition is complete, continue stirring to obtain the swollen slurry.

[0016] S3: Reduce the rotation speed to 400 rpm, add the antibacterial agent and the defoamer containing fumed silica polyether siloxane in sequence and stir; after stirring evenly, add the hydrophobic modified alkali swelling thickener and deionized water, continue stirring until the viscosity is stable, filter and discharge to obtain liquid A.

[0017] S4: Under the protection of dry nitrogen, add water-based isocyanate curing agent, molecular sieve dehydrating agent, film-forming aid, and fumed silica anti-settling agent to a dispersion tank and stir to prepare liquid B; take liquid A and liquid B and mix them evenly according to the weight ratio to obtain water-based matte antibacterial light-absorbing coating.

[0018] Furthermore, the starting stirring premixing described in S1 has a set speed range of 500~700 rpm and a stirring time of 5~12 minutes.

[0019] Furthermore, the low-speed stirring in S2 lasts for 8-12 minutes; the high-speed dispersion by increasing the rotation speed requires increasing the rotation speed to 1200-1400 rpm and dispersing at high speed for 30-40 minutes; the deionized water is slowly added to the slurry via a peristaltic pump at a drip rate of 1.0-1.5 parts / minute; and the stirring continues for 30-60 minutes.

[0020] Furthermore, as described in S3, continue stirring until the viscosity stabilizes, with a stirring time of 10-15 minutes.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) Synergistic unity of ultra-low gloss and high blackness: By constructing a four-level light trap structure, ultra-low gloss with a gloss level of 60° <0.2GU is achieved, while the blackness L value is reduced to below 15, breaking through the traditional technical formula that matte coatings will inevitably lose blackness.

[0023] (2) Synergistic effect of interface cavity and physical roughness: The micron-scale interface cavity formed by the shrinkage of swellable microspheres is introduced. The light trapping effect is enhanced by the difference in refractive index between the cavity and the resin matrix. The synergistic effect with the multi-scale physical roughness constructed by the dual-particle-size sand texture powder significantly improves the light absorption efficiency.

[0024] (3) Synergistic innovation of precise particle size distribution and in-situ swelling process: The reverse particle size distribution design is adopted so that the particle size of the microspheres after swelling is strictly smaller than that of sand texture powder A, and the volume ratio of the three is optimized to 1:2:4; combined with the dry dispersion and subsequent in-situ swelling process, the microspheres are accurately filled in the gaps of the filler, and the process has good reproducibility.

[0025] (4) Long-lasting antibacterial effect: The addition of antibacterial agents and the slow-release effect of the interface cavity make the antibacterial rate of the coating reach more than 99%. Attached Figure Description

[0026] Figure 1 This is a flowchart of a water-based matte antibacterial light-absorbing coating and its preparation method according to the present invention.

[0027] Figure 2 The following are SEM images of the coating in Experimental Example 2 of this invention: (a) cross-section of the coating; (b) surface of the coating. Detailed Implementation

[0028] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0029] The preferred embodiments of the present invention are described in detail below; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

[0030] This invention proposes a water-based matte antibacterial light-absorbing coating and its preparation method, such as... Figure 1 The diagram shown is a flowchart of a water-based matte antibacterial light-absorbing coating and its preparation method according to the present invention. The detailed preparation steps are as follows:

[0031] 1. Base material premixing and carbon black dispersion

[0032] The self-delighting waterborne hydroxyl polyurethane dispersion, polyether-modified styrene-maleic anhydride copolymer dispersant, polyether siloxane copolymer substrate wetting agent, carbon black-based waterborne color paste, and waterborne filler slurry were sequentially added to a dispersion tank and premixed at 600 rpm for 8 minutes. The mixing speed was then increased to 1400 rpm for high-speed dispersion for 25 minutes until the fineness was ≤15 μm, yielding the color paste base. The self-delighting waterborne hydroxyl polyurethane dispersion serves as the core film-forming substance, spontaneously creating surface micro-roughness after film formation, constituting the first-level light trap. The dispersant, through steric hindrance, fully deflocculates the carbon black, ensuring high blackness and stable light absorption performance. The defoamer is not added initially to avoid failure during high-speed dispersion. No additional water is added throughout the process, maintaining the system in a high-solids-content, water-free state, creating conditions for the subsequent dry dispersion of swellable microspheres.

[0033] 2. Dry dispersion and in-situ swelling of powders and swellable microspheres

[0034] Reduce the rotation speed to 400 rpm, and slowly add the dry-state swellable microspheres, textured powder A, textured powder B, and matte powder. Stir at low speed to fully mix the powder and microspheres, then increase the speed to 1300 rpm to disperse at a fineness ≤20 μm. Textured powder B, with a particle size of 100~160 μm, constructs a macroscopic rough framework as a second-level light trap. Textured powder A, with a particle size of 15~25 μm, fills the gaps in the framework to form a third-level micron-scale rough structure. Matte powder is used for fine surface modification. The swellable microspheres, in a dry state with a size of 2~8 μm, are added. Because the system has no free water, they remain dry and do not swell prematurely. They are uniformly dispersed and enter the innermost layer of the filler gaps. The rotation speed was then reduced to 600 rpm, and deionized water was slowly added dropwise through a peristaltic pump. This allowed the swellable microspheres to absorb water and swell in situ uniformly within the confined gaps of the filler to a particle size of 8-12 μm. Because the swollen particle size was strictly smaller than that of the sand texture powder A, it was automatically confined to the innermost layer of the filler gaps. During film drying, the volume of the swollen body shrank, causing interfacial debonding and forming a micron-level interfacial cavity. Its refractive index differed significantly from that of the resin matrix, thus acting as a fourth-order light trap to enhance the light-harvesting effect.

[0035] 3. Additives and final viscosity adjustment

[0036] Reduce the rotation speed to 400 rpm, add the antibacterial agent and defoamer in sequence, stir, then add the thickener and deionized water, and continue stirring until the viscosity stabilizes. Filter to obtain liquid A. The antibacterial agent provides broad-spectrum and long-lasting antibacterial function; the defoamer is added after swelling to retain its defoaming activity and avoid pinhole defects during construction; the thickener precisely controls the viscosity of the coating to ensure good leveling and anti-sagging properties during spraying.

[0037] 4. Preparation of Liquid B and Application of Coatings

[0038] Under dry nitrogen protection, waterborne isocyanate curing agent, film-forming aid, dehydrating agent, and anti-settling agent are sequentially added to a dispersion tank and stirred until uniformly dispersed to prepare liquid B. When using, liquid A and liquid B are mixed uniformly in a specific ratio to obtain a waterborne matte antibacterial light-absorbing coating. The hydroxyl groups of the self-matting polyurethane in the waterborne isocyanate curing agent and liquid A are matched at an isocyanate group / hydroxyl group (NCO / OH) equivalent ratio of 1.2~1.5:1 to ensure complete crosslinking. The dehydrating agent adsorbs trace amounts of moisture in the system to prevent side reactions between isocyanate groups and water. The film-forming aid adjusts the film-forming temperature and leveling properties of the coating film. The anti-settling agent imparts good storage stability to liquid B. After mixing liquid A and liquid B, the hydroxyl groups and isocyanate groups undergo addition polymerization to form a dense polyurethane crosslinked network, fixing the quaternary light trap structure in the coating.

[0039] The technical solution designed by this invention to solve the existing problems includes the following key points:

[0040] 1. Synergistic extinction mechanism of four-level light traps

[0041] Traditional waterborne matte coatings typically employ a single matting method, relying primarily on the scattering of light by the micro-roughness of the coating surface. However, a single matting method struggles to achieve ultra-low gloss and often comes at the cost of sacrificing blackness and coating mechanical properties. To address these technical bottlenecks, this invention constructs a four-stage light-trapping synergistic matting mechanism. Specifically, the first-stage light trap is composed of surface micro-roughness formed during the film-forming process of a self-matting waterborne hydroxyl polyurethane dispersion. This resin undergoes microphase separation through molecular chain segments. The coating surface spontaneously forms a nanoscale uneven structure with a roughness unit size of 50~200nm, providing a basic interface for light scattering. The second-level light trap is a macroscopic rough skeleton composed of textured powder B. This coarse-grained textured powder forms a surface undulation profile of hundreds of micrometers in the coating, constructing a macroscopic interface for the first diffuse reflection of light. The third-level light trap is a micrometer-level filling structure composed of textured powder A. This medium-grained textured powder fills the macroscopic undulation gaps formed by textured powder B, forming a secondary micrometer-level roughness. Together with textured powder B, it forms a continuous scale rough surface from hundreds of micrometers to tens of micrometers, effectively extending the diffuse reflection path of light on the coating surface. The fourth-level light trap is composed of micrometer-level interface cavities formed by the drying and shrinkage of swellable polymer microspheres. These microspheres are uniformly dispersed in the resin matrix in a dry state during the preparation stage of liquid A. After in-situ swelling with water in the later stage, they shrink in volume due to water evaporation during the film-forming and drying process, resulting in debonding at the interface between the microspheres and the matrix resin, thus forming a large number of micrometer-level interface cavities. The refractive index inside these cavities differs significantly from that of the surrounding resin matrix. When incident light enters the cavity, it undergoes multiple reflections and refractions on the cavity wall, significantly extending the optical path and enhancing light energy absorption, thus producing a unique light trapping effect.

[0042] The aforementioned four-level light traps continuously cover four orders of magnitude from hundreds of micrometers to micrometers in spatial scale: the first-level self-extinction resin surface micro-roughness is at the nanometer level (50~200nm), the fourth-level interface cavity is at the micrometer level (3~8μm), the third-level textured powder A is at the ten-micrometer level (15~25μm), and the second-level textured powder B is at the hundred-micrometer level (100~160μm), forming a complete light scattering-absorption network. Among them, the hundred-micrometer and ten-micrometer level structures are responsible for scattering the incident light at large angles, causing the light to be reflected multiple times on the rough surface; the nanometer level structure provides basic extinction and preferentially scatters short-wavelength blue light, avoiding the coating from turning blue; when the light enters the micrometer level interface cavity, because the cavity size is on the same order of magnitude as the wavelength of visible light, and the refractive index of the cavity and the resin matrix changes abruptly, the direction of light propagation changes drastically, and some light is trapped in the cavity and oscillates repeatedly until it is absorbed, thus achieving true light trapping rather than simple light scattering.

[0043] To verify the above-described four-level light trap structure, the coating obtained in Experiment 2 was observed using a scanning electron microscope. Figure 2 As shown, Figure 2 (a) is a cross-sectional SEM image of the coating, which clearly shows the micron-sized interface cavity (3~8μm) formed after the microspheres dried and shrank. The cavity is surrounded by a dense polyurethane matrix, confirming the existence of the fourth-order light trap. Figure 2 (b) is a SEM image of the coating surface, which clearly shows the macroscopic rough skeleton formed by the texture powder B (100~160μm), the micron-level rough structure formed by the texture powder A (15~25μm) filling the gaps in the skeleton, and the fine surface modification of the matte powder (1~5μm), confirming the existence of the second and third order light traps.

[0044] 2. Precise particle size distribution design of swellable microspheres

[0045] Traditional waterborne coatings typically employ filler systems with a single particle size or a simple mix of coarse and fine particles. The lack of precise gradation between fillers leads to low filler packing efficiency, poor coating density, and difficulty in achieving synergistic effects with functional microspheres. To address these shortcomings, this invention constructs a particle size distribution system that matches the dual-particle-size textured powder by precisely controlling the particle size of the swellable microspheres. The swellable polymer microspheres used in this invention possess controllable swelling characteristics, with their dry particle size controlled at 2-8 μm. This ensures uniform dispersion in the viscous resin system during the preparation of solution A without premature swelling. After subsequent in-situ swelling with added water, the microspheres absorb water and expand to 8-12 μm, with the swelling ratio precisely controlled at 2-3 times. In terms of particle size distribution design, this invention adopts a reverse design concept, ensuring that the swollen particle size of the microspheres is strictly smaller than the particle size of textured powder A, and consequently smaller than the particle size of textured powder B. This ensures that the microspheres can truly fill the innermost layer of the multi-level filler gaps constructed by textured powder A and textured powder B. The volume ratio of the three components was optimized to approximately 1:2:4 for microspheres:textured powder A:textured powder B, constructing a pyramid structure of nested particles from large to small. Specifically, textured powder B, with a size of 100~160μm, forms the macroscopic framework, textured powder A, with a size of 15~25μm, fills the intermediate gaps, and swellable microspheres, with a size of 8~12μm, fill the smaller gaps.

[0046] The aforementioned particle size distribution design generates a dynamic synergistic effect throughout the coating preparation process. Specifically, when the dried microspheres are uniformly dispersed, they can freely enter the gaps between the sand-textured powder particles. During water swelling, they are automatically restricted by the surrounding skeleton within the confined space, ensuring that the particle size is uniformly concentrated at 8~12μm after swelling. During film drying, due to volume shrinkage and being surrounded by the skeleton, stress concentration at the interface induces debinding, forming a 3~8μm micron cavity. This size falls precisely within the visible light wavelength range, generating a strong light trapping effect. Simultaneously, because the microspheres are located in the innermost layer of the filler gaps, the interface cavity they form effectively suppresses direct reflection of light on the filler surface, maximizing the light absorption efficiency of the carbon black colorant. This unexpectedly achieves the anomalous effect of the coating's blackness L-value increasing to below 15 instead of decreasing.

[0047] Example 1

[0048] Table 1 Raw Material Information Table

[0049]

[0050] A water-based matte antibacterial light-absorbing coating and its preparation method include the following steps:

[0051] S1: In a high-speed dispersion tank, add 55 parts of self-matting waterborne hydroxyl polyurethane dispersion, 0.9 parts of polyether modified styrene-maleic anhydride copolymer dispersant, 0.6 parts of polyether siloxane copolymer substrate wetting agent, 8 parts of carbon black-based waterborne color paste, and 20 parts of waterborne filler slurry in sequence. Start stirring and premix at 600 rpm for 8 minutes, then increase the speed to 1400 rpm for high-speed dispersion for 25 minutes to ensure that all components are fully mixed and homogeneous, thereby obtaining a high solids content base material with a solids content ≥65%.

[0052] S2: Adjust the stirring speed to 400 rpm, slowly add 3 parts of dry cross-linked polyacrylic acid-acrylate copolymer swellable microspheres, 4 parts of texture powder A, 4 parts of texture powder B, and 5 parts of matte powder. Stir at low speed for 10 minutes to fully mix the microspheres, powders, and high solids content matrix. The system contains no free water, the microspheres remain dry, and there is no premature swelling. Then increase the speed to 1300 rpm for high-speed dispersion for 35 minutes to obtain a dry dispersion slurry. Reduce the stirring speed to 600 rpm, and slowly add 8 parts of deionized water to the slurry at a rate of 1.2 parts / minute using a peristaltic pump. The swellable microspheres absorb water and swell uniformly in situ in the confined gaps of the filler. After the addition is complete, continue stirring for 45 minutes to obtain the swollen slurry.

[0053] S3: Reduce the rotation speed to 400 rpm, add 2 parts of silver-loaded zeolite molecular sieve antibacterial agent and 0.4 parts of fumed silica polyether siloxane defoamer in sequence, and stir for 8 minutes; then add 2 parts of hydrophobic modified alkali swelling thickener and 2 parts of deionized water, and continue stirring for 12 minutes until the viscosity is stable, and filter to obtain liquid A.

[0054] S4: Under dry nitrogen protection, 95 parts of water-based isocyanate curing agent, 0.6 parts of molecular sieve dehydrating agent, 6 parts of film-forming aid, and 0.3 parts of fumed silica anti-settling agent were added to a dispersion tank and stirred at 300 rpm for 25 minutes to prepare liquid B; liquid A and liquid B were mixed at a weight ratio of 7:1 and stirred at 400 rpm for 3 minutes to obtain water-based matte antibacterial light-absorbing coating.

[0055] Example 2

[0056] The preparation method is the same as in Example 1, except that:

[0057] S1: 45 parts of self-matting waterborne hydroxyl polyurethane dispersion, 0.5 parts of polyether modified styrene-maleic anhydride copolymer dispersant, 0.4 parts of polyether siloxane copolymer substrate wetting agent, 5 parts of carbon black-based waterborne color paste, and 15 parts of waterborne filler paste;

[0058] S2: 2 parts dry cross-linked polyacrylic acid-acrylate copolymer swellable microspheres, 3 parts texture powder A, 3 parts texture powder B, 4 parts matte powder, 5 parts deionized water;

[0059] S3: 1 part silver-loaded zeolite molecular sieve antibacterial agent, 0.2 parts fumed silica polyether siloxane defoamer, 1 part hydrophobic modified alkali-swelling thickener;

[0060] S4: 90 parts water-based isocyanate curing agent, 0.4 parts molecular sieve dehydrating agent, 4 parts film-forming aid, 0.2 parts fumed silica anti-settling agent, mix liquid A and liquid B at a weight ratio of 6:1;

[0061] All other steps are the same.

[0062] Example 3

[0063] The preparation method is the same as in Example 1, except that:

[0064] S1: 65 parts of self-matting waterborne hydroxyl polyurethane dispersion, 1.5 parts of polyether modified styrene-maleic anhydride copolymer dispersant, 0.8 parts of polyether siloxane copolymer substrate wetting agent, 10 parts of carbon black-based waterborne color paste, and 25 parts of waterborne filler paste;

[0065] S2: 4 parts dry cross-linked polyacrylic acid-acrylate copolymer swellable microspheres, 5 parts texture powder A, 5 parts texture powder B, 6 parts matte powder, 12 parts deionized water;

[0066] S3: 3 parts silver-loaded zeolite molecular sieve antibacterial agent, 0.6 parts fumed silica-containing polyether siloxane defoamer, and 3 parts hydrophobic modified alkali-swelling thickener;

[0067] S4: 100 parts water-based isocyanate curing agent, 0.8 parts molecular sieve dehydrating agent, 8 parts film-forming aid, 0.4 parts fumed silica anti-settling agent, mix liquid A and liquid B at a weight ratio of 8:1;

[0068] All other steps are the same.

[0069] Example 4

[0070] The preparation method is the same as in Example 1, except that:

[0071] S1: Premix at 500 rpm for 5 minutes;

[0072] S2: Stir at low speed for 8 minutes, increase the speed to 1200 rpm and disperse at high speed for 30 minutes. Slowly add it to the slurry at a rate of 1.0 part / minute, and continue stirring for 30 minutes.

[0073] S3: Continue stirring for 10 minutes until the viscosity stabilizes;

[0074] All other steps are the same.

[0075] Example 5

[0076] The preparation method is the same as in Example 1, except that:

[0077] S1: Premix at 700 rpm for 12 minutes;

[0078] S2: Stir at low speed for 12 minutes, increase the speed to 1400 rpm and disperse at high speed for 40 minutes, then slowly add it to the slurry at a rate of 1.5 parts / minute, and continue stirring for 60 minutes;

[0079] S3: Continue stirring for 15 minutes until the viscosity stabilizes;

[0080] All other steps are the same.

[0081] Example 6

[0082] The preparation method is the same as in Example 1, except that:

[0083] S1: Replace the self-maturing waterborne hydroxyl polyurethane dispersion with a self-maturing waterborne hydroxyl acrylic dispersion, with a hydroxyl value of 65 mg KOH / g and a solid content of 40%;

[0084] All other steps are the same.

[0085] Example 7

[0086] The preparation method is the same as in Example 1, except that:

[0087] S3: Replace the silver-loaded zeolite molecular sieve antibacterial agent with nano zinc oxide antibacterial agent, with a particle size of 30nm and a purity of 99.5%;

[0088] All other steps are the same.

[0089] Example 8

[0090] The preparation method is the same as in Example 1, except that:

[0091] S4: Replace the film-forming aid with dipropylene glycol butyl ether (DPNB) and use it alone;

[0092] All other steps are the same.

[0093] Comparative Example 1

[0094] A water-based two-component matte coating is prepared using a traditional process. The specific preparation process is as follows: 55 parts of self-matting waterborne hydroxyl polyurethane dispersion, 0.9 parts of dispersant, 0.6 parts of substrate wetting agent, 0.4 parts of defoamer, 8 parts of carbon black paste, and 20 parts of waterborne filler paste are mixed and dispersed evenly. 12 parts of matting powder are added and dispersed at high speed. Then, 2 parts of antifungal and bactericidal agent, 2 parts of thickener, and 10 parts of deionized water are added and stirred evenly to obtain liquid A. 95 parts of waterborne isocyanate curing agent, 0.6 parts of dehydrating agent, 6 parts of film-forming aid, and 0.3 parts of anti-settling agent are mixed evenly to obtain liquid B. When using, 117 parts of liquid A and 18 parts of liquid B are mixed to obtain the product.

[0095] Comparative Example 2

[0096] The preparation method is the same as in Example 1, except that:

[0097] S2: Omit the step of adding 3 parts of dry cross-linked polyacrylic acid-acrylate copolymer swellable microspheres;

[0098] All other steps are the same.

[0099] Comparative Example 3

[0100] The preparation method is the same as in Example 1, except that:

[0101] S2: Omit the step of adding 4 parts of texture powder A;

[0102] All other steps are the same.

[0103] Comparative Example 4

[0104] The preparation method is the same as in Example 1, except that:

[0105] S2: Omit the step of adding 4 parts of texture powder B;

[0106] All other steps are the same.

[0107] Comparative Example 5

[0108] The preparation method is the same as in Example 1, except that:

[0109] S2: Omit the step of adding 5 parts of matte powder;

[0110] All other steps are the same.

[0111] Experimental Example 1

[0112] The aqueous matte antibacterial light-absorbing coatings prepared in Examples 1-8 and Comparative Examples 1-5 were tested:

[0113] (1) 60° gloss: Referring to GB / T 9754-2025 "Determination of 20°, 60° and 85° gloss of paints and varnishes", the test sample coated with the coating of this invention is placed on a flat table. A gloss meter conforming to the standard is used, and the light source is incident at a geometric angle of 60°. At least three different positions on the sample surface are selected for measurement, and the arithmetic mean is taken as the final gloss value. To obtain reliable data, at least five parallel samples are tested in each group, and the average value is taken.

[0114] (2) Blackness L value: According to CIE1976 L a b. The measurement is performed using a uniform color space standard. During the measurement, a colorimeter conforming to national metrological standards is used. After the instrument is preheated and stabilized, it is first calibrated using a standard white plate. Then, the instrument's measuring port is tightly fitted to the coating surface, and the measurement is performed under a D65 standard light source and a 10° observation angle. The instrument automatically outputs the L value. At least five samples should be tested in each group, and the average value is taken.

[0115] (3) Antibacterial rate: Referring to GB / T 21866-2025 "Determination of Antiviral Activity and Antibacterial Properties of Coatings", the sample and the control sample without antibacterial function were sterilized by irradiation under ultraviolet light for 30 minutes. 0.1 mL of standardized bacterial solution (Staphylococcus aureus and Escherichia coli) was evenly added to the surface of the sample and the control sample, covered with a 4×4 cm sterile polyethylene film, and incubated in an incubator at 37±1℃ for 24 hours. After incubation, the surface was rinsed with sterile eluent, and the eluent was collected and serially diluted 10 times. The diluted solution was spread on nutrient agar medium and incubated for 24 hours at 37±1℃. The colony count (CFU) was counted. The antibacterial rate was calculated according to the formula R=(C0-C1) / C0×100%, where C0 is the average colony count of the control sample and C1 is the average colony count of the sample. At least 5 samples should be tested in each group, and the average value of the results should be taken.

[0116] Experiment Example 2

[0117] The coating obtained in Example 1 was sprayed onto an acrylonitrile-butadiene-styrene copolymer (ABS) substrate, and after flash drying at room temperature for 10 minutes, leveling at 60°C for 10 minutes, and curing at 80°C for 40 minutes, a coating was obtained. The coating was then fractured in liquid nitrogen, and the fracture surface was observed using a scanning electron microscope.

[0118] (1) Sample preparation for cross-sectional morphology observation: Immerse the coated ABS sample completely in liquid nitrogen for 10-15 minutes to cool it until it is completely brittle. Then take it out and break it immediately to obtain a flat original coated cross section that is not damaged by mechanical shearing. Use conductive glue to fix the brittle sample vertically on a 45° inclined sample stage so that the brittle fracture surface faces upward.

[0119] (2) Surface morphology observation sample preparation: Cut a 5mm×5mm coated sample from the cured ABS substrate, and use conductive adhesive to attach the sample flat on the SEM-specific aluminum sample stage, ensuring that the coated surface is facing up.

[0120] (3) Conductive platinum spraying treatment: Fix the sample and place it in an ion sputtering instrument to uniformly spray an extremely thin layer of conductive platinum metal with a thickness of about 2~5nm on the surface.

[0121] (4) Setting parameters: set the acceleration voltage to 10.0kV, select the secondary electronic detector as the detector type, and set the working distance to 8.0~10.0mm.

[0122] Table 2 Comparison of experimental results of Examples 1-8 and Comparative Examples 1-5

[0123]

[0124] The experimental results of Examples 1-8 and Comparative Examples 1-5 are shown in Table 2. The water-based matte antibacterial light-absorbing coating prepared by the present invention has a moderate amount of microspheres and forms an optimal particle size distribution with the dual-particle-size sand texture powder, which maximizes the synergistic effect of the four-level light trap structure and achieves the best balance between ultra-low gloss, high blackness and antibacterial durability. Therefore, it is the optimal implementation point.

[0125] Example 2 reduced the amount of self-matting resin and swellable microspheres, and correspondingly reduced the proportions of dispersant, wetting agent, color paste, filler slurry, and antibacterial agent. This resulted in a decrease in interfacial cavity density, a slight decrease in matting effect, and a corresponding increase in gloss. Example 3 increased the amount of self-matting resin and swellable microspheres, and correspondingly increased the proportions of dispersant, wetting agent, color paste, filler slurry, and antibacterial agent. This increased interfacial cavity density, enhanced light-trapping ability, and achieved optimal blackness. Example 4 used the lower limit of process parameters, shortening the premixing and high-speed dispersion time and reducing the rotation speed. This resulted in slightly insufficient filler dispersion uniformity, reduced stirring time after swelling, and a slight impact on microsphere swelling uniformity, leading to a slight decrease in overall performance. Example 5 used the upper limit of process parameters, extending the premixing and high-speed dispersion time and increasing the rotation speed. This ensured thorough deflocculation of the filler and uniform dispersion. The optimal properties were achieved with sufficient stirring time after swelling, resulting in complete and uniform swelling of the microspheres and further improved performance. In Example 6, the self-matting waterborne hydroxyl polyurethane dispersion was replaced with a self-matting waterborne hydroxyl acrylic dispersion. The self-matting effect and wetting and dispersibility of the acrylic system for carbon black were weaker than those of the polyurethane system, and both gloss and blackness were reduced. In Example 7, the silver-loaded zeolite molecular sieve antibacterial agent was replaced with a nano zinc oxide antibacterial agent. Nano zinc oxide destroys bacterial cell membranes by releasing zinc ions. Its slow-release mechanism is different from that of silver-loaded zeolite, resulting in a slight decrease in antibacterial rate, but the optical properties remained stable. In Example 8, the film-forming aid of propylene glycol methyl ether acetate and propylene glycol diacetate was replaced with a single film-forming aid of dipropylene glycol butyl ether. The solvent evaporation rate and flow parallel during the film-forming process were slightly different, but the coating gloss, blackness, and antibacterial rate were basically the same as in Example 1.

[0126] Due to the lack of key technologies, the overall performance of Comparative Examples 1-5 was reduced to varying degrees compared with the Examples. Comparative Example 1 adopted a traditional matte coating preparation process, without adding swellable microspheres, without dual-particle size sand texture powder gradation design, and without adding antibacterial agents. It relied solely on self-matting resin and matting powder for matting. The coating only had a primary and auxiliary matting structure, lacking multi-level physical roughness and interface cavities. All performance aspects were significantly inferior to the Examples of the Present Invention. Comparative Example 2 omitted swellable microspheres, that is, deleted the fourth-level light trap, and only retained the third-level physical roughness structure constructed by self-matting resin and dual-particle size sand texture powder. It lacked the refractive index difference light trap with interface cavities. The light was only scattered and could not be effectively captured and absorbed, and ultra-low gloss could not be achieved. Comparative Example 3 omits the texture powder A, i.e., removes the third-level light trap. The continuity of the particle size distribution is disrupted, and the microspheres lose the interstitial confinement of the intermediate filling structure, making it impossible to swell uniformly in the confined space. The interface cavity is unevenly formed, and the matting effect is significantly reduced. Comparative Example 4 omits the texture powder B, i.e. removes the second-level light trap. The macroscopic rough skeleton is missing, and the coating surface lacks the surface undulation profile of hundreds of micrometers. The initial diffuse reflection efficiency of light is reduced, and the insufficient surface roughness leads to a significant increase in gloss. Comparative Example 5 omits the matting powder, i.e. removes the surface fine modification layer. The surface microscale roughness is reduced, but the reduction in surface scattering actually increases the light absorption efficiency of the carbon black colorant. The blackness is better than the example, but the gloss is slightly increased.

[0127] In summary, this invention utilizes a dry dispersion-in-situ swelling process to precisely fill the gaps between the gradations of dual-size textured powder with swellable polymer microspheres. Drying and shrinkage then form micron-sized interface cavities. These cavities, along with the microphase separation of the self-matting resin and the multi-scale light scattering of the dual-size textured powder, synergistically construct a four-level light trap structure. This achieves a composite function of ultra-low gloss, high blackness light absorption, and long-lasting antibacterial properties. It overcomes the technical bottlenecks of existing technologies, such as the conflict between matting and blackness, insufficient antibacterial durability, and uncontrollable processes. This provides a water-based coating solution with both excellent optical performance and environmental durability for fields such as optical equipment housings, medical antibacterial devices, and high-end consumer electronics.

Claims

1. An aqueous matte antibacterial light absorbing coating, the light absorbing coating comprising A liquid and B liquid; characterized in that, Liquid A comprises the following components by weight: 45-65 parts of self-matting aqueous hydroxyl polymer dispersion, 0.5-1.5 parts of polyether-modified styrene-maleic anhydride copolymer dispersant, 0.4-0.8 parts of polyether siloxane copolymer substrate wetting agent, 5-10 parts of carbon black-based aqueous color paste, 15-25 parts of aqueous filler, 2-4 parts of cross-linked polyacrylic acid-acrylate copolymer swellable microspheres, 3-5 parts of texture powder A, 3-5 parts of texture powder B, 4-6 parts of matting powder, 1-3 parts of antibacterial agent, 0.2-0.6 parts of polyether siloxane copolymer defoamer containing fumed silica, 1-3 parts of hydrophobic modified alkali-swelling thickener, and 5-12 parts of deionized... Water; the raw material components of liquid B include the following components by weight: 90-100 parts of water-based isocyanate curing agent, 0.4-0.8 parts of molecular sieve dehydrating agent, 4-8 parts of film-forming aid, and 0.2-0.4 parts of fumed silica anti-settling agent; the weight ratio of liquid A and liquid B is 6:1 to 8:1; the cross-linked polyacrylic acid-acrylate copolymer swellable microspheres have a dry particle size of 2-8 μm, and after swelling in liquid A, the particle size is 8-12 μm, and the swelled particle size is smaller than that of the texture powder A; the texture powder A has a particle size of 15-25 μm; the texture powder B has a particle size of 100-160 μm.

2. The waterborne matte antimicrobial absorptive coating according to claim 1, wherein, The self-matting waterborne hydroxyl polymer dispersion is selected from one of self-matting waterborne hydroxyl polyurethane dispersion or self-matting waterborne hydroxyl acrylic dispersion, and its hydroxyl value is 60~80mgKOH / g; the waterborne isocyanate curing agent has an isocyanate group content of 16%~18%.

3. The waterborne matte antimicrobial absorptive coating according to claim 1, wherein, The antibacterial agent is one of silver-loaded zeolite molecular sieve or nano zinc oxide; the film-forming aid is selected from a compound mixture of propylene glycol methyl ether acetate and propylene glycol diacetate or dipropylene glycol butyl ether.

4. A process for the preparation of a waterborne matt antibacterial absorbing coating according to any one of claims 1 to 3, characterized in that, Specifically, the steps include the following: S1: The self-degrading waterborne hydroxyl polymer dispersion, polyether modified styrene-maleic anhydride copolymer dispersant, polyether siloxane copolymer substrate wetting agent, carbon black-based waterborne color paste, and waterborne filler are stirred and premixed, and then the speed is increased for high-speed dispersion to ensure that the components are fully mixed and uniform, thus obtaining a high solids content base material. S2: Reduce the stirring speed, add dry cross-linked polyacrylic acid-acrylate copolymer swellable microspheres, texture powder A, texture powder B, and matte powder, and stir at low speed to fully mix the microspheres, powders, and high solids content base material; then increase the speed for high-speed dispersion to obtain a dry dispersion slurry; adjust the stirring speed, add deionized water droplets into the slurry, and continue stirring after the addition is complete to obtain a swollen slurry; S3: Reduce the rotation speed, add the antibacterial agent and the defoamer containing fumed silica polyether siloxane in sequence and stir; after stirring evenly, add the hydrophobic modified alkali swelling thickener and deionized water, continue stirring until the viscosity is stable, filter and discharge to obtain liquid A; S4: Under dry nitrogen protection, water-based isocyanate curing agent, molecular sieve dehydrating agent, film-forming aid, and fumed silica anti-settling agent are stirred to prepare liquid B; liquid A and liquid B are mixed and stirred evenly to obtain water-based matte antibacterial light-absorbing coating.

5. A process for the preparation of an aqueous matt antibacterial and light absorbing coating as claimed in claim 4, wherein, The stirring premixing described in S1 has a set speed range of 500~700 rpm and a stirring time of 5~12 minutes.

6. The method for preparing a water-based matte antibacterial light-absorbing coating as described in claim 4, characterized in that, The low-speed stirring in S2 lasts for 8-12 minutes; the high-speed dispersion by increasing the rotation speed requires increasing the rotation speed to 1200-1400 rpm and dispersing at high speed for 30-40 minutes; the addition of deionized water droplets to the slurry has a drop acceleration rate of 1.0-1.5 parts / minute; and the continued stirring lasts for 30-60 minutes.

7. A process for the preparation of an aqueous matt antibacterial and light absorbing coating as claimed in claim 4, wherein, S3 continues stirring until the viscosity stabilizes, and the stirring time is 10-15 minutes.

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