Coating, preparation method and coating

Abstract

The invention provides a coating, a preparation method and a coating, the coating comprises resin, a filler and an auxiliary agent, the filler comprises first gold-plated hollow glass beads and second gold-plated hollow glass beads, and the particle size of the first gold-plated hollow glass beads is d1; the particle size of the second gold-plated hollow glass beads is d2, and d1 and d2 meet the relational expression d1 > d2; the first gold-plated hollow glass beads construct a stable heat insulation framework structure in the coating, and the second gold-plated hollow glass beads effectively fill gaps among the large-particle-size beads, so that a conduction path of heat in the coating is greatly prolonged, heat conduction is remarkably inhibited, and the overall heat conductivity coefficient is remarkably reduced; moreover, the metal layer plated on the surface of the hollow glass bead is a high-temperature-resistant and low-emissivity gold layer, and the plating layer has extremely low infrared emissivity, can effectively reflect heat radiation in a medium-high temperature environment, and remarkably weakens radiation heat transfer.

Description

Technical Field

[0001] This invention relates to the field of coating technology, specifically to a coating and its preparation method, and a coating layer. Background Technology

[0002] With the increasing demand for functional coatings in fields such as building energy conservation, aerospace, electronic equipment, and high-end decoration, composite coatings that combine excellent thermal insulation performance, lightweight properties, electromagnetic shielding capabilities, and good decorative effects have become a research hotspot. Among them, hollow glass microspheres are widely used as functional fillers due to their low density, high specific surface area, and excellent thermal insulation and dielectric properties.

[0003] Currently, coatings commonly use hollow glass microspheres with a single particle size distribution as fillers, meaning the microspheres have a narrow particle size range, primarily concentrated within a specific size range. While this single-size design facilitates process control, it has significant drawbacks in practical applications: firstly, it's difficult to achieve tight packing between microspheres, leading to uneven pore structure within the coating and affecting thermal insulation efficiency and mechanical strength; secondly, when the microsphere size is large, it easily results in a rough coating surface and poor workability; while when the particle size is too small, it's difficult to form an effective thermal barrier network, weakening overall performance. Therefore, overcoming these technical problems and defects is a key issue that needs to be addressed. Summary of the Invention

[0004] To address the problems of limited heat insulation methods and limited heat insulation effects in existing coatings, this invention provides a coating, its preparation method, and the coating layer.

[0005] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: The first aspect of the present invention provides a coating comprising a resin, a filler, and an additive. The filler comprises a first gold-plated hollow glass microsphere and a second gold-plated hollow glass microsphere. The particle size of the first gold-plated hollow glass microsphere is d1, in μm; the particle size of the second gold-plated hollow glass microsphere is d2, in μm. The d1 and the d2 satisfy the relationship d1 > d2.

[0006] Optionally, the value of d1 is in the range of 30 to 50 and / or the value of d2 is in the range of 5 to 10.

[0007] Optionally, the filler further includes aerogel, wherein the mass ratio of the first gold-plated hollow glass microspheres, the second gold-plated hollow glass microspheres and the aerogel is 1:(0.2~0.4):(0.2~0.4).

[0008] Optionally, the mass ratio of the filler, the resin, and the additive is 1:(1.5~3):(0.1~0.5).

[0009] Optionally, the coating may also include a solvent, wherein the solid content of the coating is 30% to 50%.

[0010] Optionally, the resin includes one or more of organic resins and inorganic resins; and / or, the additives include dispersants and anti-settling agents.

[0011] A second aspect of the present invention provides a method for preparing a coating, the method comprising the following steps: Obtain the first gold-plated hollow glass microspheres and the second gold-plated hollow glass microspheres; The resin and the additives are mixed and ground until the particle size is less than 2 μm. Then the filler is added and stirred evenly to obtain the coating.

[0012] Optionally, the preparation method of the first gold-plated hollow glass microspheres and the second gold-plated hollow glass microspheres includes the following steps: Hollow glass microspheres with particle sizes satisfying d1 and d2 were selected; Hollow glass microspheres are placed in an alkaline solution with a mass concentration of 2% to 10% and stirred at 30 to 60°C for 1 to 3 hours to complete the alkaline washing. After drying the alkaline-washed microbeads, they are placed in hydrogen peroxide for hydroxylation treatment; or, after drying the alkaline-washed microbeads, they are placed in an acidic solution for acid washing treatment. The hollow glass microspheres were added to the gold plating solution and stirred at 50-90°C for 30-120 minutes to complete the gold plating.

[0013] Optionally, the gold plating solution includes a gold source, a reducing agent, and a complexing agent, wherein the gold source is selected from chloroauric acid; the reducing agent is selected from one or more of sodium hypophosphite, formaldehyde, sodium borohydride, or glucose; and the complexing agent is selected from one or more of sodium citrate or EDTA.

[0014] A third aspect of the present invention provides a coating obtained by applying and curing a coating as described above, or by applying and curing a coating prepared by the coating preparation method described above.

[0015] According to the coating provided by the present invention, by simultaneously introducing first gold-plated hollow glass microspheres (d1) and second gold-plated hollow glass microspheres (d2) with different particle sizes into the coating, wherein d1>d2, the first gold-plated hollow glass microspheres construct a stable heat-insulating skeleton structure in the coating, while the second gold-plated hollow glass microspheres effectively fill the gaps between the large-diameter microspheres, thereby significantly extending the heat conduction path inside the coating, significantly inhibiting heat conduction, and significantly reducing the overall thermal conductivity. Moreover, the metal layer coated on the surface of the hollow glass microspheres is a high-temperature resistant, low-emissivity gold layer. This coating has extremely low infrared emissivity and can effectively reflect thermal radiation in medium and high-temperature environments, significantly weakening radiative heat transfer, especially exhibiting excellent infrared shielding capability in the temperature range of 200–600℃. The present invention achieves efficient heat insulation from both conduction and radiation, the two main heat transfer pathways, through the synergistic effect of structural design (dual-diameter graded microspheres) and functional materials (surface gold plating), breaking through the performance bottleneck of traditional single-mechanism heat insulation materials. Detailed Implementation

[0016] To make the technical problems solved, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0017] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; the materials and reagents used are commercially available unless otherwise specified.

[0018] In one embodiment, the first aspect of the present invention provides a coating comprising a resin, a filler, and an additive. The filler comprises a first gold-plated hollow glass microsphere and a second gold-plated hollow glass microsphere. The particle size of the first gold-plated hollow glass microsphere is d1 in μm, and the particle size of the second gold-plated hollow glass microsphere is d2 in μm. d1 and d2 satisfy the relationship d1 > d2.

[0019] For ease of description, in the following text, "first gold-plated hollow glass microspheres" and "second gold-plated hollow glass microspheres" will be collectively referred to as "gold-plated hollow glass microspheres".

[0020] By simultaneously introducing first gold-plated hollow glass microspheres (d1) and second gold-plated hollow glass microspheres (d2) with different particle sizes into the coating, where d1>d2, the first gold-plated hollow glass microspheres construct a stable heat-insulating skeleton structure in the coating, while the second gold-plated hollow glass microspheres effectively fill the gaps between the large-diameter microspheres. This significantly extends the heat conduction path within the coating, significantly inhibits heat conduction, and noticeably reduces the overall thermal conductivity. Moreover, the metal layer coated on the surface of the hollow glass microspheres is a high-temperature resistant, low-emissivity gold layer. This coating has extremely low infrared emissivity, which can effectively reflect thermal radiation in medium- and high-temperature environments, significantly weakening radiative heat transfer, especially exhibiting excellent infrared shielding capabilities in the temperature range of 200–600℃. This invention achieves efficient heat insulation through the synergistic effect of structural design (dual-diameter graded microspheres) and functional materials (surface gold plating), simultaneously achieving efficient heat insulation from both conduction and radiation, the two main heat transfer pathways, breaking through the performance bottleneck of traditional single-mechanism heat insulation materials.

[0021] In one embodiment, the value of d1 ranges from 30 to 50.

[0022] Specifically, the value of d1 is any one value or any two values ​​from 30, 32, 34, 36, 38, 40, 42, 44, 46, 48 or 50; in a preferred embodiment, the value of d1 is 35 to 45.

[0023] When the value of d1 is in the range of 30~50, a thermal insulation skeleton with a stable structure and reasonable pore distribution can be formed in the coating. At the same time, it can achieve efficient graded filling with the second gold-plated hollow glass microspheres with smaller particle size, maximize the extension of the heat conduction path and reduce internal convection. Thus, while ensuring the mechanical strength of the coating, the thermal conductivity is significantly reduced, and good construction performance and surface smoothness are maintained, resulting in the best overall thermal insulation effect. When the value of d1 is less than 30, the "skeleton" effect of large-diameter microspheres weakens, making it difficult to effectively construct a continuous low thermal conductivity network. This results in small-diameter microspheres not being fully confined and orderly filled, leading to a denser overall pore structure but limited improvement in thermal resistance, and the insulation performance not reaching its optimal level. At the same time, the increased total specific surface area of ​​the microspheres may increase the difficulty of resin encapsulation, affecting the stability and film density of the coating. When the value of d1 is greater than 50, although the insulation capacity of individual microspheres is enhanced, they are prone to sedimentation, agglomeration, or uneven distribution in the coating, damaging the uniformity of the coating and reducing adhesion and mechanical strength. In addition, excessively large particle sizes will significantly increase the surface roughness of the coating, affecting workability and appearance quality. Furthermore, the excessively large gaps between microspheres may weaken the filling effect of small-diameter microspheres, thus reducing the overall thermal resistance. In some cases, stress concentration at high temperatures may even cause microcracks, damaging long-term insulation stability.

[0024] In one embodiment, the value of d2 ranges from 5 to 10.

[0025] Specifically, the value of d2 is any one value or any two values ​​from 5, 6, 7, 8, 9 or 10; in a preferred embodiment, the value of d2 is 6 to 9.

[0026] When the value of d2 is in the range of 5 to 10, its size is adapted to the gap between the skeleton formed by the first gold-plated hollow glass microspheres, which can efficiently fill the pores between the large microspheres, significantly reduce the air convection channels inside the coating and further extend the heat conduction path; at the same time, the microspheres in this particle size range have good dispersibility and resin wettability, which helps to form a dense, uniform and low thermal conductivity composite coating structure, maximizing the heat insulation effect without sacrificing mechanical properties. When d2 is less than 5, the specific surface area of ​​the microspheres increases dramatically, leading to a higher demand for resin encapsulation. This can cause increased system viscosity and decreased flowability, affecting the coating's application performance. Simultaneously, excessively fine microspheres tend to agglomerate, making it difficult to disperse evenly in the matrix. Instead, they form high-density areas locally, weakening the gradation filling effect and reducing the thermal insulation efficiency of the porous structure. Furthermore, nano- or submicron-sized particles may sinter or become unstable at high temperatures, affecting the long-term thermal stability of the coating. When d2 is greater than 10, the difference between its particle size and d1 narrows, making it unable to effectively embed into the gaps of the large microsphere skeleton. This results in decreased filling efficiency, leaving more interconnected pores, shortening the heat conduction path, and weakening the thermal insulation performance. At the same time, the advantage of the bimodal particle size distribution is weakened, and the coating tends towards a single coarse particle stacking structure. This not only reduces thermal resistance but may also increase solid-phase heat conduction due to the increased contact points between particles, offsetting the thermal insulation advantages of hollow microspheres.

[0027] In one embodiment, the filler further includes aerogel, and the mass ratio of the first gold-plated hollow glass microspheres, the second gold-plated hollow glass microspheres and the aerogel is 1:(0.2~0.4):(0.2~0.4).

[0028] Specifically, the aerogel includes one or more of silica aerogel, hydrophobically modified silica aerogel, carbon aerogel, alumina aerogel, and composite aerogel; the composite aerogel includes one or more of SiO2 / Al2O3 aerogel and SiO2 / TiO2 aerogel; in a preferred embodiment, the aerogel is selected from hydrophobically modified silica aerogel. The hydrophobically modified silica aerogel is a surface-modified version of ordinary silica aerogel (e.g., reacted with hexamethyldisilazane, trimethylchlorosilane, etc.); thereby significantly improving hydrophobicity and dispersion stability, and preventing moisture absorption and aggregation in coatings.

[0029] Specifically, the mass ratio of the first gold-plated hollow glass microspheres, the second gold-plated hollow glass microspheres, and the aerogel is any one of the following ratios or a range of any two ratios: 1:0.2:0.2, 1:0.3:0.2, 1:0.4:0.2, 1:0.2:0.3, 1:0.3:0.3, 1:0.4:0.3, 1:0.2:0.4, 1:0.3:0.4, or 1:0.4:0.4; in a preferred embodiment, the mass ratio of the first gold-plated hollow glass microspheres, the second gold-plated hollow glass microspheres, and the aerogel is 1:0.3:0.3.

[0030] When the mass ratio of the first gold-plated hollow glass microspheres, the second gold-plated hollow glass microspheres, and the aerogel is 1:(0.2~0.4):(0.2~0.4), the three components form a multi-scale synergistic thermal insulation structure in the coating: the large-diameter first gold-plated hollow glass microspheres construct a stable low thermal conductivity framework; the small-diameter second gold-plated hollow glass microspheres effectively fill the medium-sized pores between the large microspheres; and the nanoporous aerogel further penetrates and fills the tiny gaps and interfacial voids that the micron-sized microspheres cannot cover. This three-level gradation structure maximizes the extension of the heat conduction path, inhibits gas convection and solid-phase conduction, and significantly reduces the overall thermal conductivity of the coating. Simultaneously, the gold plating layer provides excellent low infrared emissivity, effectively reflecting medium- and high-temperature thermal radiation and significantly weakening radiative heat transfer. Therefore, under this ratio, the coating exhibits both ultra-low thermal conductivity and strong infrared shielding capability under medium- and high-temperature conditions of 200–600℃, achieving dual high-efficiency blocking of both conductive and radiative heat transfer, resulting in optimal overall thermal insulation performance. When the mass ratio of the first gold-plated hollow glass microspheres, the second gold-plated hollow glass microspheres, and the aerogel is less than 1:0.4:0.4, that is, when the proportion of the second gold-plated hollow glass microspheres and / or the aerogel is too high, the excessive amount of the second gold-plated hollow glass microspheres will disrupt the continuity of the skeleton of the first gold-plated hollow glass microspheres, leading to excessive dilution of the resin in the coating and insufficient binder phase, thereby reducing the mechanical strength and adhesion of the coating. At the same time, excessive aerogel content can easily cause a sharp increase in the viscosity of the system, making dispersion difficult, and may form thermal bridges due to moisture absorption or agglomeration, which will weaken the thermal insulation effect and increase the cost. When the mass ratio of the first gold-plated hollow glass microspheres, the second gold-plated hollow glass microspheres, and aerogel is greater than 1:0.2:0.2, that is, when the proportion of the second gold-plated hollow glass microspheres and / or aerogel is too low, the pores between the skeletons of the first gold-plated hollow glass microspheres are not fully filled, leaving more interconnected channels, shortening the heat conduction path, enhancing air convection, and leading to an increase in thermal conductivity. At the same time, insufficient aerogel results in a lack of nanoscale thermal insulation contribution, failing to fully utilize its ultra-low thermal conductivity advantage, and the overall thermal insulation performance does not meet design expectations, especially in terms of limited radiative heat transfer suppression effect at high temperatures.

[0031] In one embodiment, the mass ratio of filler, resin and additives is 1:(1.5~3):(0.1~0.5).

[0032] Specifically, the mass ratio of filler, resin, and additives is any one of the following: 1:1.5:0.1, 1:2:0.1, 1:2.5:0.1, 1:3:0.1, 1:1.5:0.3, 1:2:0.3, 1:2.5:0.3, 1:3:0.3, 1:1.5:0.5, 1:2:0.5, 1:2.5:0.5, or 1:3:0.5, or a range of any two of these ratios; in a preferred embodiment, the mass ratio of filler, resin, and additives is 1:(2~2.5):0.3.

[0033] When the mass ratio of filler, resin, and additives is 1:(1.5~3):(0.1~0.5), the resin content is moderate enough to fully wet and encapsulate the high proportion of filler, forming a continuous and dense film-forming network. This ensures the coating has good adhesion, flexibility, and mechanical strength. Furthermore, a reasonable additive ratio effectively controls the system's rheology, dispersion stability, defoaming, and leveling properties, preventing filler sedimentation or agglomeration. Simultaneously, while ensuring film quality, maximizing the filler volume fraction fully leverages the low thermal conductivity structure and low emissivity surface characteristics of the multi-scale filler synergistic construction, enabling the coating to possess both ultra-low thermal conductivity and strong infrared radiation shielding capabilities at 200–600℃, achieving highly efficient thermal insulation. When the mass ratio of filler, resin, and additives is less than 1:3:0.5, excessive resin will dilute the filler concentration, reduce the content of the thermal insulation functional phase per unit volume, and weaken the thermal resistance network constructed by the microsphere skeleton and aerogel. Excessive amounts of organic resin can lead to increased thermal conductivity and decreased insulation performance. Excessive organic resin may undergo thermal decomposition, carbonization, or softening at high temperatures, reducing the thermal stability and long-term reliability of the coating. Excessive additives may introduce unnecessary small molecule residues, affecting coating density and even causing bubbles or pinholes, damaging insulation integrity and durability. When the mass ratio of filler, resin, and additives is greater than 1:1.5:0.1, the resin is insufficient to completely coat the high specific surface area filler (especially aerogels and second gold-plated hollow glass microspheres), resulting in uneven filler dispersion, easy agglomeration or sedimentation, and the appearance of pores, interface defects, or stress concentration points within the coating. Poor film continuity, significantly reduced adhesion, flexibility, and crack resistance make it prone to peeling and failure under thermal cycling or mechanical vibration. Insufficient additives make it difficult to control the viscosity and leveling of high-solids systems, leading to difficult construction, rough and uneven coating surfaces, further affecting insulation performance and appearance quality.

[0034] In one embodiment, the coating also includes a solvent, and the solid content in the coating is 30% to 50%.

[0035] In some embodiments, the solvent includes one or more of alcohol solvents, water, ether solvents, or ester solvents.

[0036] Alcohol solvents include one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, ethylene glycol monobutyl ether, or benzyl alcohol.

[0037] Ether solvents include one or more of ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether (BCS), diethylene glycol monomethyl ether, propylene glycol methyl ether (PMA), dipropylene glycol methyl ether (DPM), tetrahydrofuran (THF), and 1,4-dioxane.

[0038] Ester solvents include one or more of ethyl acetate, n-butyl acetate, isobutyl acetate, sec-butyl acetate, propylene glycol methyl ether acetate (PMAc), ethyl lactate, and γ-butyrolactone.

[0039] Specifically, the solid content in the coating is any one value or a range of any two values ​​from 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, 46%, 48%, or 50%; in a preferred embodiment, the solid content in the coating is 34%-46%.

[0040] When the solid content in the coating is 30%~50%, the filler can reach the critical volume fraction required for effective heat insulation, forming a multi-level porous structure in the coating of "large microsphere skeleton - small microsphere filling - aerogel nano-sealing". This significantly extends the heat conduction path, inhibits gas convection, and, combined with the low infrared emissivity of the gold plating layer, achieves efficient blocking of both conduction and radiation heat transfer mechanisms. The resin content is sufficient to completely wet the high specific surface area filler and form a continuous and dense film-forming network, ensuring the adhesion, cohesive strength, and thermal shock resistance of the coating at high temperatures of 200–600℃. The system has moderate viscosity and good rheological properties, suitable for various construction methods such as spraying, brushing, or roller coating. During the drying process, solvent release is stable, and pinholes, edge shrinkage, or surface defects are not easily generated. Surface defects; while ensuring thermal insulation performance, it also takes into account storage stability and construction efficiency, with reasonable single-coat film thickness and high overall cost performance; when the solid content in the coating is less than 30%, the total amount of functional fillers is insufficient, making it impossible to construct an effective multi-scale thermal insulation network, resulting in low coating thermal resistance, difficulty in reducing thermal conductivity to the ideal level, and significantly weakened thermal insulation performance; when the solvent ratio is too high, the number of coatings required per unit dry film increases, construction efficiency is low, and VOC emissions are relatively high; although the fluidity is good, the economy is poor, making it difficult to meet the dual requirements of high performance and high efficiency for industrial thermal insulation; when the solid content in the coating is greater than 50%, the system viscosity rises sharply, the fluidity and construction performance are severely deteriorated, and problems such as poor spray atomization, brush stringing, and difficulty in leveling are likely to occur.

[0041] In one embodiment, the resin includes one or more of organic resins and inorganic resins.

[0042] In some embodiments, the organic resin includes one or more of polyurethane, polyvinyl chloride, epoxy resin, and phenolic resin; In some embodiments, the inorganic resin is selected from a mixture of organoalkoxysilane compounds and silica sol. Specifically, the organoalkoxysilane compounds are selected from one or more of tetraethyl orthosilicate (TEOS), methyltriethoxysilane (MTES), and vinyltrimethoxysilane (VTMS). Organoalkoxysilane compounds are mixed with silica sol in a certain proportion and then hydrolyzed and polycondensed in situ to form a three-dimensional Si–O–Si network structure. It has excellent high temperature resistance, excellent compatibility with filler interfaces, and good compatibility with metal substrates, effectively suppressing cracking and peeling under high temperature cycling. It can optimize the reflection / scattering behavior of the coating on infrared radiation and work synergistically with the gold plating layer to further suppress radiative heat transfer.

[0043] In one embodiment, the additives include dispersants and antisettling agents.

[0044] In some embodiments, the dispersant includes one or more of the following: polymeric dispersants, anionic / nonionic surfactants, phosphate ester dispersants, and silane coupling agents as auxiliary dispersants; Specifically, polymeric dispersants include one or more of polyacrylates (such as BYK®-P104, Disperbyk®-190) and polyurethane block copolymers (such as BYK®-2000, Tego® Dispers750W); Anionic / nonionic surfactants include one or more of alkylphenol polyoxyethylene ether sulfates and fatty alcohol polyoxyethylene ethers; Phosphate ester dispersants include phosphate ester-modified acrylic copolymers; Silane coupling agents are one or more of γ-aminopropyltriethoxysilane and γ-methacryloyloxypropyltrimethoxysilane.

[0045] Dispersants reduce the surface energy of fillers by adsorbing onto their surfaces, preventing particle agglomeration; they also form steric hindrance or electrostatic repulsion in the resin matrix, improving the dispersion uniformity and long-term stability of high specific surface area fillers; they improve the interfacial compatibility between fillers and resins, enhance wettability, reduce bubble encapsulation, and improve coating density; and they effectively reduce system viscosity, maintaining good fluidity even under high solids content conditions, which is beneficial for construction and film formation.

[0046] Specifically, anti-settling agents include one or more of the following: organic bentonite, fumed silica, polyamide wax, hydrogenated castor oil derivatives, and inorganic thickeners and anti-settling agents.

[0047] The anti-settling agent forms a weak gel or thixotropic network structure when left to stand, effectively inhibiting the settling and hardening of high-density fillers; preventing local functional loss caused by filler delamination, and ensuring the uniformity of coating performance.

[0048] This invention significantly improves the dispersion uniformity and storage stability of multiphase filler systems by adding dispersants and anti-settling agents to coatings, avoiding agglomeration, sedimentation, or flocculation; it can also maintain the appropriate rheological properties of coatings under high solids content conditions; ensure that the designed multi-scale thermal insulation structure is formed inside the coating, give full play to the synergistic effect of "skeleton-filler-nanopore sealing", and maximize the reduction of thermal conductivity; avoid local thermal bridges or mechanical weaknesses caused by uneven filler distribution, and improve the overall thermal insulation performance, adhesion, and durability of the coating.

[0049] In one embodiment, a second aspect of the present invention provides a method for preparing a coating, the method comprising the following steps: S1. Obtain the first gold-plated hollow glass microsphere and the second gold-plated hollow glass microsphere; S2. Mix the resin and additives, grind until the particle size is less than 2 μm, then add the filler and stir evenly to obtain the coating.

[0050] Specifically, in step S2, mixing the resin and additives also includes adding a solvent and aerogel; Aerogels tend to form hard aggregates (with particle sizes reaching tens of micrometers) in their original state, making them difficult to disperse evenly when added directly. By co-grinding with resin and solvent to a particle size of less than 2 μm, their secondary agglomeration structure can be effectively broken, allowing them to be evenly distributed in the matrix in a state close to primary particles. This maximizes their ultra-low thermal conductivity and avoids the thermal bridging effect caused by agglomeration.

[0051] The ground aerogel slurry is fully integrated with resin and additives to form a highly stable premixed liquid, providing a good wetting and encapsulation base for the subsequent addition of gold-plated hollow glass microspheres. This prevents the surface of the gold-plated hollow glass microspheres from being covered by aerogel clumps, which would affect the coating function or interfacial bonding. Moreover, the nanoscale dispersed aerogel can effectively fill the submicron-level pores between the gold-plated hollow glass microspheres and the voids at the resin-filler interface, further extending the heat conduction path, inhibiting gas convection and solid-phase heat conduction, and synergistically constructing a "macro-meso-nano" three-level thermal insulation network with the gold-plated hollow glass microsphere skeleton, thereby significantly reducing the overall thermal conductivity of the coating.

[0052] In one embodiment, the preparation method of the first gold-plated hollow glass microspheres and the second gold-plated hollow glass microspheres includes the following steps: Hollow glass microspheres with particle sizes satisfying d1 and d2 were selected; Hollow glass microspheres are placed in an alkaline solution with a mass concentration of 2% to 10% and stirred at 30 to 60°C for 1 to 3 hours to complete the alkaline washing. After drying the alkaline-washed microbeads, they are placed in hydrogen peroxide for hydroxylation treatment; or, after drying the alkaline-washed microbeads, they are placed in an acidic solution for acid washing treatment. The hollow glass microspheres were added to the gold plating solution and stirred at 50-90°C for 30-120 minutes to complete the gold plating.

[0053] Specifically, alkaline solutions include, but are not limited to, one or more of sodium hydroxide or potassium hydroxide.

[0054] The gold-plated hollow glass microsphere preparation process of the present invention significantly improves the cleanliness, activity and metal bonding of the microsphere surface through a multi-step synergistic treatment of alkaline washing – surface activation (hydroxylation or acid washing roughening) – chemical gold plating, thereby endowing it with excellent functionality and stability.

[0055] Hydroxylation treatment is beneficial for the uniform adsorption and reduction of gold ions in subsequent electroless plating processes; Pickling and roughening treatment can form a nanoscale micro-rough structure, increase the specific surface area, and further enhance the bonding strength between the metal coating and the substrate through mechanical interlocking.

[0056] The two activation pathways can be flexibly selected according to the polarity of the resin system or the construction requirements, taking into account both chemical bonding and physical anchoring mechanisms.

[0057] The reaction is carried out in a chemical gold plating solution at 50-90℃ for 30-120 minutes. Gold ions (such as those from chloroauric acid) are selectively reduced by a reducing agent on the surface of activated hollow glass microspheres, forming a continuous and dense metallic gold layer. This coating has extremely low infrared emissivity, which can efficiently reflect thermal radiation in the temperature range of 200-600℃, significantly suppressing radiative heat transfer. It also has high temperature resistance and oxidation resistance, and is stable for a long time in medium and high temperature environments without significant discoloration or peeling. Furthermore, it is firmly bonded to the hollow glass microsphere matrix, ensuring the functional integrity of the filler in the coating system and ensuring that it continues to play a thermal insulation skeleton role in the coating.

[0058] Specifically, acidic solutions include one or more of dilute sulfuric acid, dilute hydrochloric acid, and dilute nitric acid.

[0059] In one embodiment, the gold plating solution includes a gold source, a reducing agent, and a complexing agent. The gold source is selected from chloroauric acid; the reducing agent is selected from one or more of sodium hypophosphite, formaldehyde, sodium borohydride, or glucose; and the complexing agent is selected from one or more of sodium citrate or EDTA.

[0060] Gold readily dissociates into Au in aqueous solution. 3+The gold ions possess excellent solubility and stability, ensuring uniform release and providing a reliable source for forming a dense, continuous, and high-purity metallic gold coating on the surface of hollow glass microspheres. The resulting coating exhibits excellent infrared reflectivity and low emissivity, effectively suppressing thermal radiation heat transfer within the temperature range of 200–600℃.

[0061] The multi-element reducing agent system enables a controllable, efficient, and gentle reduction process. By using it alone or in combination, the gold plating rate, coating morphology, and crystallinity can be flexibly controlled, balancing efficiency and coating quality. The presence of the complexing agent ensures that the gold plating reaction occurs only on the surface of the activated microspheres, achieving autocatalytic selective deposition and avoiding the waste of gold powder and loose coating caused by homogeneous nucleation.

[0062] The synergistic effect of the above components enables the gold plating solution to form a gold plating layer with strong adhesion, dense uniformity, low emissivity and high temperature resistance on the surface of hollow glass microspheres under mild conditions of 50–90℃ and 30–120 minutes. The plating solution also has good stability and high reusability, making it suitable for large-scale production.

[0063] In one embodiment, a third aspect of the present invention provides a coating obtained by applying and curing a coating as described above, or by applying and curing a coating prepared by the coating preparation method described above.

[0064] The coating provided by this invention not only breaks through the performance bottleneck of traditional single-mechanism thermal insulation materials, but also achieves a high degree of unity between thermal insulation efficiency, temperature adaptability, structural stability and engineering feasibility, making it an ideal solution for medium and high temperature thermal insulation in the 200–600℃ range.

[0065] The beneficial effects of the present invention will be further illustrated below with reference to the embodiments.

[0066] To make the inventive objectives, technical solutions, and beneficial effects of this invention clearer, the invention is further described in detail below with reference to embodiments. However, it should be understood that the embodiments of this invention are merely for illustrative purposes and not for limiting the invention, and the embodiments are not limited to those given in the specification. Unless otherwise specified, the materials in the embodiments were prepared under conventional conditions or according to the conditions recommended by the material supplier.

[0067] Furthermore, it should be understood that the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps, does not preclude the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps, unless otherwise stated. It should also be understood that the combined connection relationship between one or more devices / apparatus mentioned in this invention does not preclude the existence of other devices / apparatus before or after the combined devices / apparatus, or the insertion of other devices / apparatus between these explicitly mentioned devices / apparatus, unless otherwise stated. Moreover, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not for limiting the order of the method steps or limiting the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0068] In the following embodiments, the reagents, materials and instruments used, unless otherwise specified, are commercially available or can be obtained through synthesis methods known in the art.

[0069] Table 1. Design of coating parameters for Examples 1-27 and Comparative Examples 1-3; Example 1 This embodiment illustrates the coating disclosed in this invention; it includes the following operational steps: Hollow glass microspheres with particle sizes d1 and d2 are selected. The hollow glass microspheres are placed in a sodium hydroxide solution with a mass concentration of 2% to 10% and stirred at 30 to 60°C for 1 to 3 hours to complete the alkaline washing. After the alkaline washing, the microspheres are dried and then placed in hydrogen peroxide for hydroxylation treatment; or, after the alkaline washing, the microspheres are dried and then placed in an acidic solution for acid washing treatment. After drying, the hollow glass microspheres are added to the gold plating solution and stirred at 50 to 90°C for 30 to 120 minutes to complete the gold plating.

[0070] The resin, solvent, and additives were mixed, and aerogel was added. The mixture was ground until the particle size was less than 2 μm. Then, large-diameter gold-plated hollow glass microspheres and small-diameter gold-plated hollow glass microspheres were added and stirred until homogeneous.

[0071] Example 2-27 Examples 2-27 illustrate the coatings disclosed in this invention, including most of the operational steps in Example 1, with the following differences: The parameters of the coatings shown in Table 1 are used.

[0072] Comparative Examples 1-3 Comparative Examples 1-3 are used to illustrate the coatings disclosed in this invention, including most of the operational steps in Example 1, the difference being: The parameters of the coatings shown in Table 1 are used.

[0073] Performance testing The following performance tests were performed on the batteries prepared in Examples 1-27 and Comparative Examples 1-3: Thermal conductivity test: The transient plane heat source method is adopted. The available testing equipment is Hot Disk TPS 2500S (equipped with a 600℃ high temperature furnace). The testing method refers to the standard GB / T 32064-2015.

[0074] Infrared emissivity testing: High-temperature blackbody comparison method (differential measurement), available testing equipment: SETARAM SEP3000, testing method reference standards GB / T 21089-2007, GJB 5023.2-2003. The test results are shown in Table 2.

[0075] Table 2 Coating Performance Examples and Comparative Examples Comparing Examples 1-3, Examples 6-7, and Comparative Example 1, it can be seen that when d1 and d2 satisfy the relationship d1>d2, the thermal conductivity is as low as 0.007-0.012W / (m·K) and the emissivity is as low as 0.07-0.10, which is a better performance; when d1<d2, the thermal conductivity is 0.032W / (m·K) and the emissivity is 0.26, there is no effective heat insulation skeleton, and the gold plating layer is unevenly distributed.

[0076] Comparing Examples 1-3, 6-7, and Comparative Examples 2-3, it can be seen that when the coating contains both the first gold-plated hollow glass microspheres and the second gold-plated hollow glass microspheres, its thermal conductivity is as low as 0.007-0.012 W / (m·K), and its emissivity is as low as 0.07-0.10, exhibiting superior performance. When the coating contains only the first gold-plated hollow glass microspheres, its thermal conductivity is 0.035 W / (m·K), and its emissivity is 0.32. It contains only large-diameter microspheres, with no gap filling, resulting in excessive heat conduction channels and insufficient radiation reflection area. When the coating contains only the second gold-plated hollow glass microspheres, its thermal conductivity is 0.043 W / (m·K), and its emissivity is 0.12. It contains only small-diameter microspheres, without large-diameter skeleton support, resulting in high coating density and increased thermal conductivity.

[0077] Comparing Examples 1-5, it can be seen that when the value of d1 is in the range of 30~50, its thermal conductivity is as low as 0.007-0.009 W / (m·K) and its emissivity is as low as 0.07-0.09, with better performance; when the value of d1 is less than 30, its thermal conductivity is as low as 0.015 W / (m·K) and its emissivity is as low as 0.15, the continuity of the skeleton is insufficient, and the local thermal bridging effect is obvious; when the value of d1 is greater than 50, its thermal conductivity is as low as 0.017 W / (m·K) and its emissivity is as low as 0.17, the first gold-plated hollow glass microspheres are slightly agglomerated, and the pore connectivity is slightly improved.

[0078] Comparing Examples 1 and 6-9, it can be seen that when the value of d2 is in the range of 5~10, its thermal conductivity is as low as 0.007-0.012 W / (m·K) and its emissivity is as low as 0.07-0.10, showing better performance. When the value of d2 is less than 5, its thermal conductivity is as low as 0.018 W / (m·K) and its emissivity is as low as 0.18, and the second gold-plated hollow glass microspheres slightly agglomerate, forming a local high-density heat conduction zone. When the value of d2 is greater than 10, its thermal conductivity is as low as 0.020 W / (m·K) and its emissivity is as low as 0.19, and the second gold-plated hollow glass microspheres cannot be completely embedded in the gaps between the first gold-plated hollow glass microspheres, with the filling efficiency dropping to 60%.

[0079] Comparing Examples 1 and 10-16, it can be seen that when the mass ratio of the first gold-plated hollow glass microspheres, the second gold-plated hollow glass microspheres, and the aerogel is 1:(0.2~0.4):(0.2~0.4), the thermal conductivity is as low as 0.007-0.010 W / (m·K), and the emissivity is as low as 0.07-0.09, indicating good performance. When the mass ratio of the first gold-plated hollow glass microspheres, the second gold-plated hollow glass microspheres, and the aerogel deviates from 1:(0.2~0.4):(0.2~0.4), the thermal conductivity drops to 0.010-0.013 W / (m·K), and the emissivity drops to 0.10-0.13, showing a sharp decline in performance. When the aerogel is absent in the coating, the thermal conductivity drops to 0.022. With an emissivity of 0.20 W / (m·K), the nanoscale pores of the first and second gold-plated hollow glass microspheres are not blocked, which enhances the thermal conduction effect between the gaps.

[0080] Comparing Examples 1 and 17-24, it can be seen that when the mass ratio of filler, resin, and additives is 1:(1.5~3):(0.1~0.5), the thermal conductivity is as low as 0.007-0.008 and the emissivity is as low as 0.07-0.08, showing good performance. When the mass ratio of filler, resin, and additives deviates from 1:3:0.5, the thermal conductivity drops to 0.014-0.024 W / (m·K) and the emissivity drops to 0.08-0.15, showing a sharp drop in performance. When there is no resin in the coating, film cannot be formed. When there is no additive in the coating, the thermal conductivity drops to 0.025 W / (m·K) and the emissivity drops to 0.28. In the absence of additives in the coating, the filler slightly agglomerates and settles, resulting in poor uniformity of the coating's performance and making it impossible to form a uniform heat insulation / reflection structure.

[0081] Comparing Examples 1, 10, and 25-27, it can be seen that when the solid content in the coating is 30%~50%, its thermal conductivity is as low as 0.007-0.010 and its emissivity is as low as 0.07-0.10, indicating good performance. When the solid content in the coating is less than 30%, its thermal conductivity is as low as 0.012 W / (m·K) and its emissivity is as low as 0.12, indicating insufficient filler content and incomplete thermal insulation framework construction. When the solid content in the coating is greater than 50%, its thermal conductivity is as low as 0.018 W / (m·K) and its emissivity is as low as 0.12, indicating high system viscosity and the generation of a small number of microbubble defects during film formation, affecting emissivity and thermal insulation effect.

[0082] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A coating characterized by: The material includes resin, filler, and additives. The filler includes a first gold-plated hollow glass microsphere and a second gold-plated hollow glass microsphere. The particle size of the first gold-plated hollow glass microsphere is d1, in μm; the particle size of the second gold-plated hollow glass microsphere is d2, in μm. The d1 and d2 satisfy the relationship d1>d2.

2. The coating of claim 1, wherein: The value of d1 is in the range of 30 to 50; and / or the value of d2 is in the range of 5 to 10.

3. The coating of claim 1, wherein: The filler also includes aerogel, and the mass ratio of the first gold-plated hollow glass microspheres, the second gold-plated hollow glass microspheres and the aerogel is 1:(0.2~0.4):(0.2~0.4).

4. The coating of claim 1, wherein: The mass ratio of the filler, the resin, and the additive is 1:(1.5~3):(0.1~0.5).

5. The coating of claim 1, wherein: It also includes solvents, and the solid content in the coating is 30% to 50%.

6. The coating of claim 1, wherein: The resin includes one or more of organic resins and inorganic resins; and / or the additives include dispersants and anti-settling agents.

7. The process for the preparation of a coating according to any one of claims 1 to 6, characterized in that: The preparation method includes the following steps: Obtain the first gold-plated hollow glass microspheres and the second gold-plated hollow glass microspheres; The resin and the additives are mixed and ground until the particle size is less than 2 μm. Then the filler is added and stirred evenly to obtain the coating.

8. The method of claim 7, wherein: The preparation methods of the first gold-plated hollow glass microspheres and the second gold-plated hollow glass microspheres include the following steps: Hollow glass microspheres with particle sizes satisfying d1 and d2 are selected; the hollow glass microspheres are placed in an alkaline solution with a mass concentration of 2%~10% and stirred at 30~60℃ for 1~3 hours to complete the alkaline washing; after drying the alkaline-washed microspheres, they are placed in hydrogen peroxide for hydroxylation treatment; or, after drying the alkaline-washed microspheres, they are placed in an acidic solution for acid washing treatment; the above hollow glass microspheres are added to the gold plating solution and stirred at 50~90℃ for 30~120 minutes to complete the gold plating.

9. The method of claim 8, wherein: The gold plating solution includes a gold source, a reducing agent, and a complexing agent. The gold source is selected from chloroauric acid; the reducing agent is selected from one or more of sodium hypophosphite, formaldehyde, sodium borohydride, or glucose; and the complexing agent is selected from one or more of sodium citrate or EDTA.

10. A coating characterized by: The coating obtained by applying and curing the coating as described in any one of claims 1-6, or the coating obtained by applying and curing the coating prepared by the coating preparation method as described in any one of claims 7-9.

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