A glass reflective thermal barrier paint

Abstract

The application relates to the functional coating technical field and discloses a glass reflection heat insulation paint, which comprises A component and B component; the A component comprises, in mass percentage, 45.0%-55.0% of solvent type hydroxyl acrylic resin, 5.0%-8.0% of hexagonal system nanometer cesium tungsten bronze powder, 1.0%-2.5% of anchoring type high molecular super dispersant, 0.2%-0.6% of cerium isooctoate, 0.8%-1.5% of bis (1-octyloxy-2, 2, 6, 6-tetramethyl-4-piperidyl) sebacate, 0.1%-0.3% of a leveling agent and the rest of mixed solvents; and the B component is aliphatic hexamethylene diisocyanate trimer. The application effectively inhibits the photochromic phenomenon of the coating and does not interfere with the crosslinking and curing. In combination with a step-by-step in-situ modification preparation process, competition of metal ions for coordination is avoided, secondary agglomeration of the powder is prevented, and the visible light transmission ratio of the paint film and the heat storage stability of the paint are improved.

Description

Technical Field

[0001] This invention relates to the field of functional coatings technology, specifically to a glass reflective heat-insulating paint. Background Technology

[0002] Hexagonal cesium tungsten bronze nanoparticles possess excellent near-infrared blocking properties due to their specific crystal structure, and are widely used in transparent reflective heat-insulating coatings for architectural and automotive glass. However, this material exhibits significant photochromic defects under long-term ultraviolet irradiation. Photogenerated electrons, stimulated within its crystal lattice, tend to accumulate at surface defects, causing hexavalent tungsten to be reduced to pentavalent tungsten. This polaron generation leads to the broadening of the original infrared absorption peak into the visible light region, macroscopically manifesting as a sharp decrease in coating transmittance and a darkening of the color.

[0003] To suppress the discoloration caused by photogenerated electrons and the aging of the resin matrix, existing technologies typically add hindered amine light stabilizers to the system. However, in two-component polyurethane coating systems composed of hydroxyl acrylic resin and isocyanate curing agents, the conventional hindered amine molecular structure usually contains active hydrogen atoms of the secondary amine. These active hydrogen atoms have strong nucleophilicity and readily undergo competitive chemical addition reactions with isocyanate groups at room temperature to form urea bonds. This unintended side reaction not only ineffectively consumes the curing agent but also hinders the normal stepwise addition polymerization reaction between the resin hydroxyl groups and isocyanate groups, resulting in the inability of the coating film to form a complete and dense three-dimensional network. Ultimately, this leads to low crosslinking density and severe deterioration of adhesion and physical strength.

[0004] Furthermore, to ensure the thermal insulation coating has high visible light transmittance and low transmittance haze, it is necessary to rely on polymeric superdispersants to coat the nano-cesium tungsten bronze powder to provide steric hindrance, stabilizing it at the tens of nanometers particle size level. Further attempts to introduce transition metal compounds with high electrode potentials (to preferentially capture photogenerated electrons to suppress discoloration) generally face the engineering challenge of the dispersion system's tendency to collapse. Because conventional processes often employ a preparation method of directly grinding the mixed components, the free, strongly coordinated transition metal ions in the system preferentially compete for coordination with the anchoring groups of the polymeric dispersant. This strong complexation disrupts the original binding force between the dispersant and the nanoparticle surface, causing a large amount of dispersant macromolecules to desorb from the inorganic particle surface. The nanoparticles, deprived of external steric protection, inevitably undergo secondary agglomeration. The volume expansion of these micro-agglomerates hinders relative slippage within the fluid, causing a sharp increase in the coating's dynamic viscosity or even direct gelation, resulting in the complete loss of the product's thermal storage stability and application performance. Therefore, how to simultaneously block the photochromic mechanism, avoid interference with cross-linking and curing, and maintain the long-term anti-agglomeration stability of nano-pigments in a two-component system is a technical challenge that urgently needs to be solved in this field. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a glass reflective heat-insulating paint that solves the problems of secondary agglomeration of nano-cesium tungsten bronze powder in two-component polyurethane heat-insulating coating systems, photochromism caused by ultraviolet irradiation, and low crosslinking density of the paint film due to interference from conventional hindered amine additives in isocyanate curing and crosslinking.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] This invention provides a glass reflective heat-insulating paint, which adopts the following technical solution:

[0008] A glass reflective heat-insulating paint includes component A and component B; the components of component A, by mass percentage, include: solvent-based hydroxyl acrylic resin: 45.0%-55.0%; hexagonal crystalline nano-cesium tungsten bronze powder: 5.0%-8.0%, with the molecular formula Cs. x WO3, where x is 0.30-0.33; anchoring polymeric superdispersant: 1.0%-2.5%; cerium isooctanoate: 0.2%-0.6%; sebacic acid bis-1-octoxy-2,2,6,6-tetramethyl-4-piperidinyl ester: 0.8%-1.5%; leveling agent: 0.1%-0.3%; mixed solvent: balance, to 100%; the B component is an aliphatic hexamethylene diisocyanate trimer; the molar ratio of the hydroxyl groups of the solvent-type hydroxy acrylic resin in the A component to the isocyanate groups of the aliphatic hexamethylene diisocyanate trimer in the B component is 1:1.05-1:1.15.

[0009] By employing the above technical solution, and by combining cerium isooctanoate with sebacic acid bis-1-octoxy-2,2,6,6-tetramethyl-4-piperidinyl ester (which contains no active hydrogen molecules), and by controlling the molar ratio of the curing groups within a set range, the coating achieves resistance to photochromism and maintains a high crosslinking density. The specific reaction mechanism is implemented through the following steps:

[0010] The first step involves generating photogenerated electron-hole pairs within the hexagonal cesium tungsten bronze nanolattice under ultraviolet irradiation.

[0011] In the second step, the tetravalent cerium ions in cerium isooctanoate possess a high electrode potential, preferentially capturing photogenerated electrons on the surface of cesium tungsten bronze at the mesoscale, and then reducing themselves to trivalent cerium ions. This step cuts off the enrichment pathway of free electrons at lattice defects, blocks the polaron generation reaction that reduces hexavalent tungsten to pentavalent tungsten, thereby suppressing the broadening of the coating's infrared absorption peak into the visible light region and macroscopic discoloration.

[0012] In the third step, sebacic acid bis-1-octoxy-2,2,6,6-tetramethyl-4-piperidinyl-ester re-oxidizes trivalent cerium ions to tetravalent cerium ions through a free radical cycle regeneration mechanism, completing the mediator regeneration and solid-phase electron relay consumption, and keeping the electron spin exchange channel open.

[0013] In the fourth step, during the two-component curing and crosslinking stage, the nitrogen atom of the piperidine ring in sebacic acid bis-1-octoxy-2,2,6,6-tetramethyl-4-piperidinyl ester is replaced by an alkoxy group, resulting in a molecular structure without secondary amine active hydrogen atoms, thus exhibiting chemical inertness to the isocyanate groups in component B. The isocyanate groups within the system only undergo a stepwise addition polymerization reaction with the hydroxyl groups of the hydroxyl acrylic resin in component A, forming urethane crosslinks. This mechanism avoids the conventional nucleophilic addition competition reaction between hindered amines and curing agents, prevents urea bond end-capping, and ensures the formation of a dense three-dimensional crosslinked network in the two-component paint film.

[0014] Preferably, the anchoring polymeric superdispersant is an acrylate block copolymer containing a tertiary amine anchoring group, and the monomers of the anchoring polymeric superdispersant include at least methyl methacrylate, butyl acrylate, and N,N-dimethylaminoethyl methacrylate. The mass ratio of cerium isooctanoate to sebacic acid bis-1-octoxy-2,2,6,6-tetramethyl-4-piperidinyl ester is 1:2.5-1:4.5. The cerium isooctanoate and the sebacic acid bis-1-octoxy-2,2,6,6-tetramethyl-4-piperidinyl ester are anchored to the periphery of the Stern layer on the surface of the hexagonal cesium tungsten bronze nanoparticles by intermolecular van der Waals entanglement with the hydrophobic tail of the anchoring polymeric superdispersant, forming a heterogeneous redox gradient layer on the mesoscopic scale of component A.

[0015] By employing the above technical solution, the tertiary amine groups of the anchored polymeric superdispersant undergo hydrogen bonding and acid-base interactions with the surface of hexagonal cesium tungsten bronze nanoparticles. The polymeric chain segments construct a steric hindrance layer around the powder, preventing physical contact between the nanoparticles. The specific component ratio and van der Waals entanglement confine the active components within a specific spatial hierarchy. While maintaining the repulsive barrier between particles on the powder surface, this shortens the physical transfer path of photogenerated electrons across the phase interface, thus enhancing the electron trapping effect.

[0016] Preferably, the mixed solvent is a solvent in which propylene glycol methyl ether acetate and butyl acetate are mixed in a mass ratio of 1:1; the solvent-based hydroxyl acrylic resin has a solid content of 70% and a hydroxyl mass fraction of 3.0%; the cerium mass fraction in the cerium isooctanoate is 10%-12%; and the leveling agent is polyether-modified polydimethylsiloxane.

[0017] By adopting the above technical solution, a mixed solvent with specific solubility parameters and a resin system with corresponding solid content are set, ensuring the mutual solubility of each functional component in the continuous phase and the rheological stability of the coating film formation stage.

[0018] This invention also provides a method for preparing a glass reflective heat-insulating paint, using the following technical solution:

[0019] A method for preparing a glass reflective heat-insulating paint includes the following steps:

[0020] The first step involves mixing the mixed solvent and the anchoring polymer superdispersant evenly, then adding hexagonal crystalline nano-cesium tungsten bronze powder for high-speed shear dispersion, followed by pumping it into a horizontal closed sand mill for circulating grinding until the median particle size of the slurry reaches 40nm-60nm to obtain nano-color paste. Cerium isooctanoate and sebacic acid bis-1-octoxy-2,2,6,6-tetramethyl-4-piperidinyl-ester are not added at this stage.

[0021] The second step is to transfer the nano-color paste into the reactor and adjust the stirring speed to 300 rpm-500 rpm;

[0022] The third step involves pre-mixing cerium isooctanoate and sebacic acid bis-1-octoxy-2,2,6,6-tetramethyl-4-piperidinyl ester in propylene glycol methyl ether acetate to form a complex solution.

[0023] The fourth step involves adding the complexing solution to the nano-color paste in the reactor at a dropping rate of 1.0 kg / min to 2.0 kg / min, controlling the temperature inside the reactor at 30℃ to 40℃, and continuously stirring for 1.5 to 2.0 hours to obtain the modified slurry.

[0024] Fifth step: pre-add solvent-based hydroxyl acrylic resin to the paint mixing tank and start stirring, then slowly add modified slurry and leveling agent, stir and filter to obtain component A;

[0025] Step 6: Seal and package component A and the aliphatic hexamethylene diisocyanate trimer (component B) separately. Mix component A and component B before final use.

[0026] By adopting the above technical solution, due to the stepwise in-situ modification process, only mixed solvents, polymeric superdispersants, and inorganic powders exist in the system during the early stage of grinding, allowing the superdispersant to preferentially coat the powder surface. In the later stage of grinding, cerium isooctanoate complexing solution is introduced to prevent tetravalent cerium ions with strong coordination capabilities from preferentially coordinating with tertiary amine groups on the dispersant molecules under mechanical shearing. Eliminating the competitive coordination reaction of metal ions prevents the dispersant from desorbing from the inorganic powder surface, maintains the spatial isolation mechanism between nanoparticles, avoids the increase in the volume of microparticle aggregates leading to fluid relative slippage and macroscopic dynamic viscosity increase and gelation, and ensures the rheological stability and thermal storage life of the coating.

[0027] Preferably, the specific process parameters for obtaining the nano-color paste are as follows: Add a mixed solvent and an anchoring polymeric superdispersant to a mixing tank, and stir at 500 rpm-800 rpm for 15-20 minutes; uniformly and batch-wise add hexagonal cesium tungsten bronze nanoparticles, increase the speed to 1500 rpm-2000 rpm, and perform high-speed dispersion for 45-60 minutes; fill a horizontal closed sand mill with 0.1 mm-0.3 mm zirconium oxide beads, control the grinding liquid temperature at 25℃-35℃, set the linear speed of the grinding rotor to 10 m / s-12 m / s, and perform circulating grinding for 3-5 hours. After adding solvent-based hydroxyl acrylic resin to the paint mixing tank, start stirring at 600 rpm-800 rpm, slowly add the modified slurry, and after adding the leveling agent, continue stirring for 30-45 minutes.

[0028] By adopting the above technical solution and setting parameters for mechanical shear force, grinding media size, and temperature control, the powder is fully pulverized without secondary aggregation. The median particle size is much smaller than the visible light wavelength, reducing the Mie scattering effect and ensuring high transmittance and low transmission haze of the coating in the visible light band.

[0029] Preferably, the specific synthesis steps of the anchoring polymeric superdispersant include: heating 30.0 parts by weight of propylene glycol methyl ether acetate to 90℃-95℃; mixing 40.0 parts by weight of methyl methacrylate, 20.0 parts by weight of butyl acrylate, 10.0 parts by weight of N,N-dimethylaminoethyl methacrylate, and 1.5 parts by weight of azobisisobutyronitrile to prepare a monomer mixture; adding the monomer mixture dropwise to propylene glycol methyl ether acetate at a constant temperature of 90℃-95℃ for 3.0-3.5 hours; maintaining the temperature for 1.0 hour, adding 0.2 parts by weight of azobisisobutyronitrile dissolved in propylene glycol methyl ether acetate, continuing to maintain the temperature for 2.0 hours, cooling to below 40℃, and filtering out the material.

[0030] By adopting the above technical solution, controlling the specific monomer ratio and the constant temperature dropwise polymerization sequence, the conversion rate of the polymerization reaction is ensured, and block copolymers with a clear distribution of hydrophobic segments and anchoring groups are prepared, providing a stable physical structural basis for the dispersion system.

[0031] This invention provides a glass reflective heat-insulating paint. It has the following beneficial effects:

[0032] 1. This invention constructs a heterogeneous redox gradient layer on the surface of cesium tungsten bronze powder by introducing cerium isooctanoate and sebacic acid bis(1-octoxy-2,2,6,6-tetramethyl-4-piperidinyl) ester (without active hydrogen) into component A. Cerium isooctanoate preferentially captures photogenerated electrons to inhibit the reduction of hexavalent tungsten, while the hindered amine with this specific structure regenerates cerium ions through free radical cycling, thus effectively solving the photochromic problem of nano-cesium tungsten bronze under ultraviolet light. Simultaneously, the hindered amine molecule is chemically inert to the isocyanate group, avoiding competitive consumption reactions with component B, and ensuring the high crosslinking density and physical strength of the two-component polyurethane coating.

[0033] 2. This invention employs a stepwise in-situ modification process to prepare the color paste. First, an anchoring polymeric superdispersant is used to physically grind and disperse the powder. After forming a stable nano-color paste, a complex solution of cerium isooctanoate and hindered amine is added dropwise. This process sequence fundamentally avoids competition for coordination between the strongly coordinating tetravalent cerium ions and the tertiary amine groups of the dispersant, preventing the desorption of dispersant macromolecules from the powder surface. This maintains the steric barrier between nanoparticles, solving the problem of secondary agglomeration of inorganic powders and the resulting increase in the dynamic viscosity of the coating, significantly extending the product's thermal storage life.

[0034] 3. This invention independently synthesizes an acrylate block copolymer containing tertiary amine groups as a superdispersant, which can form high-strength hydrogen bonds and acid-base anchoring with the surface of hexagonal cesium tungsten bronze nanoparticles. Combined with defined grinding media size and linear velocity parameters, the median particle size of the slurry is precisely controlled within the 40nm-60nm range. This combination of material structure and process parameters minimizes the Mie scattering effect of nanoparticles within the paint film, enabling the heat-insulating paint to maintain a high infrared blocking rate while possessing a high visible light transmittance and low transmission haze. Attached Figure Description

[0035] Figure 1 This is a graph showing the change in dynamic viscosity during the grinding process according to an embodiment of the present invention.

[0036] Figure 2 This is a graph showing the change in dynamic viscosity during the grinding process according to an embodiment of the present invention.

[0037] Figure 3 This is a comparative diagram of the curing reaction kinetics process in an embodiment of the present invention;

[0038] Figure 4 This is a comparison chart of crosslinking density (gel fraction) after coating curing according to embodiments of the present invention;

[0039] Figure 5 This is a comparison of the spectral transmittance curves of the cured coating film in the 380-2500 nm wavelength range according to an embodiment of the present invention.

[0040] Figure 6 This is a comparison diagram of the transmission haze of the cured coating films in various embodiments and comparative examples of the present invention;

[0041] Figure 7 This is a graph showing the attenuation of visible light transmittance as a function of irradiation time, according to an embodiment of the present invention.

[0042] Figure 8 This is a graph showing the change in coating color difference value with irradiation time according to an embodiment of the present invention.

[0043] Figure 9 This is a comparison diagram of dynamic viscosity before and after thermally accelerated aging in an embodiment of the present invention;

[0044] Figure 10 This is a comparison diagram of the median diameter D50 before and after thermally accelerated aging in an embodiment of the present invention. Detailed Implementation

[0045] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0046] Preparation Examples 1-4:

[0047] Preparation Example 1: This preparation example provides a method for preparing an anchored polymeric superdispersant, including the following steps:

[0048] In a four-necked flask equipped with a reflux condenser, a mechanical stirrer, and a nitrogen protection device, add 30.0 parts by weight of propylene glycol methyl ether acetate, start stirring and heat to 90℃-95℃;

[0049] 40.0 parts by weight of methyl methacrylate, 20.0 parts by weight of butyl acrylate, 10.0 parts by weight of N,N-dimethylaminoethyl methacrylate and 1.5 parts by weight of azobisisobutyronitrile were uniformly mixed to prepare a monomer mixture.

[0050] Under constant temperature conditions of 90℃-95℃, the monomer mixture was added dropwise to propylene glycol methyl ether acetate at a constant rate, and the addition time was controlled at 3.0-3.5 hours.

[0051] After the addition was complete, the reaction was kept at this temperature for 1.0 hour; then 0.2 parts by mass of azobisisobutyronitrile dissolved in a small amount of propylene glycol methyl ether acetate was added, and the reaction was kept at this temperature for another 2.0 hours.

[0052] Cool the material down to below 40°C, filter it, and you will get an anchored polymeric superdispersant with a solid content of 70% (mass fraction).

[0053] Preparation Example 2: This preparation example provides a method for preparing an anchored polymeric superdispersant, including the following steps:

[0054] In a four-necked flask equipped with a reflux condenser, a mechanical stirrer, and a nitrogen protection device, add 30.0 parts by weight of propylene glycol methyl ether acetate, start stirring and heat to 92℃-94℃;

[0055] 45.0 parts by weight of methyl methacrylate, 15.0 parts by weight of butyl acrylate, 10.0 parts by weight of N,N-dimethylaminoethyl methacrylate and 1.2 parts by weight of azobisisobutyronitrile were uniformly mixed to prepare a monomer mixture.

[0056] Under constant temperature conditions of 92℃-94℃, the monomer mixture was added dropwise to propylene glycol methyl ether acetate at a constant rate over a period of 3.2 hours.

[0057] After the addition was complete, the reaction was kept at the temperature for 1.0 hour; then 0.15 parts by weight of azobisisobutyronitrile dissolved in a small amount of propylene glycol methyl ether acetate was added, and the reaction was kept at the temperature for another 2.5 hours.

[0058] Cool the material down to below 40°C, filter it, and you will get an anchored polymeric superdispersant with a solid content of 70% (mass fraction).

[0059] Preparation Example 3: This preparation example provides a method for preparing an anchored polymeric superdispersant, including the following steps:

[0060] In a four-necked flask equipped with a reflux condenser, a mechanical stirrer, and a nitrogen protection device, add 30.0 parts by weight of propylene glycol methyl ether acetate, start stirring and heat to 90℃-92℃;

[0061] 35.0 parts by weight of methyl methacrylate, 20.0 parts by weight of butyl acrylate, 15.0 parts by weight of N,N-dimethylaminoethyl methacrylate and 1.8 parts by weight of azobisisobutyronitrile were uniformly mixed to prepare a monomer mixture.

[0062] Under constant temperature conditions of 90℃-92℃, the monomer mixture was added dropwise to propylene glycol methyl ether acetate at a constant rate over a period of 3.5 hours.

[0063] After the addition was complete, the reaction was kept at the temperature for 1.5 hours; then 0.25 parts by weight of azobisisobutyronitrile dissolved in a small amount of propylene glycol methyl ether acetate was added, and the reaction was kept at the temperature for another 2.0 hours.

[0064] Cool the material down to below 40°C, filter it, and you will get an anchored polymeric superdispersant with a solid content of 70% (mass fraction).

[0065] Preparation Example 4: This preparation example provides a method for preparing an anchored polymeric superdispersant, including the following steps:

[0066] In a four-necked flask equipped with a reflux condenser, a mechanical stirrer, and a nitrogen protection device, add 30.0 parts by weight of propylene glycol methyl ether acetate, start stirring and heat to 94℃-95℃;

[0067] 38.0 parts by weight of methyl methacrylate, 25.0 parts by weight of butyl acrylate, 7.0 parts by weight of N,N-dimethylaminoethyl methacrylate and 1.0 part by weight of azobisisobutyronitrile were uniformly mixed to prepare a monomer mixture.

[0068] Under constant temperature conditions of 94℃-95℃, the monomer mixture was added dropwise to propylene glycol methyl ether acetate at a constant rate, and the addition time was controlled at 3.0 hours.

[0069] After the addition was complete, the reaction was kept at the temperature for 1.0 hour; then 0.1 parts by mass of azobisisobutyronitrile dissolved in a small amount of propylene glycol methyl ether acetate was added, and the reaction was kept at the temperature for another 3.0 hours.

[0070] Cool the material down to below 40°C, filter it, and you will get an anchored polymeric superdispersant with a solid content of 70% (mass fraction).

[0071] Examples 1-4:

[0072] Example 1: This example provides a glass reflective heat-insulating paint and its preparation method, including the following steps:

[0073] 1) By mass percentage, 24.0% of propylene glycol methyl ether acetate and 23.9% of butyl acetate were mixed evenly, and 1.0% of the anchoring polymeric superdispersant prepared in Preparation Example 1 was added. The mixture was stirred at 600 rpm for 18 minutes.

[0074] Subsequently, 5.0% of hexagonal cesium tungsten bronze nanoparticles were added in batches at a uniform speed, and the rotation speed was increased to 1600 rpm for high-speed dispersion for 50 minutes. The slurry was then pumped into a horizontal closed sand mill, filled with 0.1 mm-0.3 mm zirconium oxide beads, and ground at a temperature of 28°C with a grinding rotor linear speed of 10 m / s for 3 hours to obtain a nano-color paste with a D50 particle size of 45 nm. Cerium isooctanoate and sebacic acid bis(1-octoxy-2,2,6,6-tetramethyl-4-piperidinyl) ester were not added at this stage.

[0075] 2) Transfer the nano-color paste to the reaction vessel and adjust the stirring speed to 400 rpm; mix 0.2% cerium isooctanoate and 0.8% sebacic acid bis(1-octoxy-2,2,6,6-tetramethyl-4-piperidinyl) ester in 1.0% propylene glycol methyl ether acetate to form a complex solution.

[0076] 3) The complexing solution was added to the nano-color paste in the reactor at a dropping rate of 1.2 kg / min, the temperature inside the reactor was controlled at 35℃, and the mixture was stirred continuously for 1.8 hours to obtain the modified slurry;

[0077] 4) Add 45.0% solvent-based hydroxyl acrylic resin to the paint mixing tank, turn on the stirring speed of 700 rpm, slowly add the modified slurry, and add 0.1% polyether-modified polydimethylsiloxane. After stirring for 40 minutes, filter through a 200-mesh filter to obtain component A.

[0078] 5) Add aliphatic hexamethylene diisocyanate trimer as component B according to the molar ratio of hydroxyl groups to isocyanate groups of resin in component A of 1:1.05, mix and then cure on the surface of glass substrate to form a film.

[0079] Example 2: This example provides a glass reflective heat-insulating paint and its preparation method, including the following steps:

[0080] 1) By mass percentage, 18.5% of propylene glycol methyl ether acetate and 18.4% of butyl acetate were mixed evenly, and 1.8% of the anchoring polymeric superdispersant prepared in Preparation Example 2 was added. The mixture was stirred at 800 rpm for 20 minutes. Then, 6.5% of hexagonal crystalline nano-cesium tungsten bronze powder was added in batches at a uniform speed, and the speed was increased to 2000 rpm for high-speed dispersion for 60 minutes. The slurry was pumped into a horizontal closed sand mill, filled with 0.1 mm-0.3 mm zirconia beads, and the temperature was controlled at 32°C. The mill was circulated and ground at a grinding rotor linear speed of 11 m / s for 4 hours to obtain a nano-color paste with a D50 particle size of 52 nm. Cerium isooctanoate and sebacic acid bis(1-octoxy-2,2,6,6-tetramethyl-4-piperidinyl) ester were not added at this stage.

[0081] 2) Transfer the nano-color paste to the reaction vessel and adjust the stirring speed to 500 rpm; mix 0.4% cerium isooctanoate and 1.2% sebacic acid bis(1-octoxy-2,2,6,6-tetramethyl-4-piperidinyl) ester in 1.5% propylene glycol methyl ether acetate to form a complex solution.

[0082] 3) The complexing solution was added to the nano-color paste in the reactor at a dropping rate of 1.5 kg / min, the temperature inside the reactor was controlled at 38℃, and the mixture was stirred continuously for 2.0 hours to obtain the modified slurry;

[0083] 4) Add 50.0% solvent-based hydroxyl acrylic resin to the paint mixing tank, turn on the stirring speed to 800 rpm, slowly add the modified slurry, and add 0.2% polyether-modified polydimethylsiloxane. After stirring for 45 minutes, filter through a 200-mesh filter to obtain component A.

[0084] 5) Add aliphatic hexamethylene diisocyanate trimer as component B according to the molar ratio of hydroxyl groups to isocyanate groups of resin in component A of 1:1.10, mix and then cure on the surface of glass substrate to form a film.

[0085] Example 3: This example provides a glass reflective heat-insulating paint and its preparation method, including the following steps:

[0086] 1) By mass percentage, 14.5% of propylene glycol methyl ether acetate and 14.3% of butyl acetate were mixed evenly, and 2.5% of the anchoring polymeric superdispersant prepared in Preparation Example 3 was added. The mixture was stirred at 500 rpm for 15 minutes. Then, 8.0% of hexagonal crystalline nano-cesium tungsten bronze powder was added in batches at a uniform speed, and the speed was increased to 1800 rpm for high-speed dispersion for 45 minutes. The slurry was pumped into a horizontal closed sand mill, filled with 0.1 mm-0.3 mm zirconia beads, and the temperature was controlled at 35 °C. The mill was circulated and ground at a grinding rotor linear speed of 12 m / s for 5 hours to obtain a nano-color paste with a D50 particle size of 58 nm. Cerium isooctanoate and sebacic acid bis(1-octoxy-2,2,6,6-tetramethyl-4-piperidinyl) ester were not added at this stage.

[0087] 2) Transfer the nano-color paste to the reaction vessel and adjust the stirring speed to 300 rpm; mix 0.6% cerium isooctanoate and 1.5% sebacic acid bis(1-octoxy-2,2,6,6-tetramethyl-4-piperidinyl) ester in 2.0% propylene glycol methyl ether acetate to form a complex solution.

[0088] 3) The complexing solution was added to the nano-color paste in the reactor at a dropping rate of 2.0 kg / min, the temperature inside the reactor was controlled at 40℃, and the mixture was stirred continuously for 1.5 hours to obtain the modified slurry;

[0089] 4) Add 55.0% solvent-based hydroxyl acrylic resin to the paint mixing tank, turn on the stirring speed to 600 rpm, slowly add the modified slurry, and add 0.3% polyether-modified polydimethylsiloxane. After stirring for 30 minutes, filter through a 200-mesh filter to obtain component A.

[0090] 5) Add aliphatic hexamethylene diisocyanate trimer as component B according to the molar ratio of hydroxyl groups to isocyanate groups of resin in component A of 1:1.15, mix and cure on the surface of glass substrate to form a film.

[0091] Example 4: This example provides a glass reflective heat-insulating paint and its preparation method, including the following steps:

[0092] 1) By mass percentage, 21.0% of propylene glycol methyl ether acetate and 21.0% of butyl acetate were mixed evenly, and 2.0% of the anchoring polymeric superdispersant prepared in Preparation Example 4 was added. The mixture was stirred at 700 rpm for 20 minutes. Then, 6.0% of hexagonal crystalline nano-cesium tungsten bronze powder was added in batches at a uniform speed, and the speed was increased to 1500 rpm for high-speed dispersion for 60 minutes. The mixture was then circulated and ground in a horizontal closed sand mill for 4 hours to obtain a nano-color paste with a D50 particle size of 48 nm. Cerium isooctanoate and sebacic acid bis(1-octoxy-2,2,6,6-tetramethyl-4-piperidinyl) ester were not added at this stage.

[0093] 2) Transfer the nano-color paste to the reaction vessel and adjust the stirring speed to 450 rpm; mix 0.3% cerium isooctanoate and 1.35% sebacic acid bis(1-octoxy-2,2,6,6-tetramethyl-4-piperidinyl) ester (mass ratio 1:4.5) in 1.2% propylene glycol methyl ether acetate to form a complex solution;

[0094] 3) The complexing solution was added to the nano-color paste in the reactor at a dropping rate of 1.0 kg / min, the temperature inside the reactor was controlled at 32℃, and the mixture was stirred continuously for 2.0 hours to obtain the modified slurry;

[0095] 4) Add 47.0% solvent-based hydroxyl acrylic resin to the paint mixing tank, turn on the stirring speed of 750 rpm, slowly add the modified slurry, and add 0.15% polyether-modified polydimethylsiloxane. After stirring for 35 minutes, filter through a 200-mesh filter to obtain component A.

[0096] 5) Add aliphatic hexamethylene diisocyanate trimer as component B according to the molar ratio of hydroxyl groups to isocyanate groups of resin in component A of 1:1.10, mix and then cure on the surface of glass substrate to form a film.

[0097] Comparative Examples 1-6:

[0098] Comparative Example 1: Compared with Example 2, the difference is that cerium isooctanoate is not added to the formulation of component A, and its mass percentage difference is made up by the mixed solvent. Furthermore, the pre-complexation operation of cerium isooctanoate in steps 2) and 3) is not performed. All other aspects are the same.

[0099] Comparative Example 2: Compared with Example 2, the difference is that: bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidinyl) sebacate is not added to the A component formulation, and its mass percentage difference is made up by the mixed solvent. The pre-complexation operation of this substance in steps 2) and 3) is not performed. All other aspects are the same.

[0100] Comparative Example 3: Compared with Example 2, the difference is that the bis(1-octoxy-2,2,6,6-tetramethyl-4-piperidinyl) sebacate in component A was replaced by an equal mass of bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, and all other aspects were the same.

[0101] Comparative Example 4: Compared with Example 2, the difference is that cerium isooctanoate in component A was replaced by iron acetylacetone in equal mass, while the rest were the same.

[0102] Comparative Example 5: Compared with Example 2, the difference is that steps 1), 2), and 3) are omitted. Solvent-based hydroxyl acrylic resin, mixed solvent, anchoring polymer superdispersant, cerium isooctanoate, sebacate bis(1-octoxy-2,2,6,6-tetramethyl-4-piperidinyl) ester, and hexagonal crystalline nano-cesium tungsten bronze powder are added sequentially to the paint mixing tank. After high-speed dispersion, the powder is directly pumped into a sand mill and ground until the D50 particle size is 52 nm. Then, polyether-modified polydimethylsiloxane leveling agent is added and the mixture is filtered to obtain component A. All other steps are the same.

[0103] Comparative Example 6: Compared with Example 2, the difference lies in the high-speed dispersion and initial grinding stage in step 1), where cerium isooctanoate and sebacic acid bis(1-octoxy-2,2,6,6-tetramethyl-4-piperidinyl) ester are directly added to the mixing tank and subjected to high-shear grinding without media interference together with hexagonal cesium tungsten bronze nanoparticles; the low-shear complexation and dropwise addition process in steps 2) and 3) is omitted, and after grinding reaches the standard, it is directly transferred to the paint mixing tank for step 4), and the rest are the same.

[0104] Test Examples 1-5:

[0105] Test Example 1:

[0106] To verify whether the stepwise process can avoid competition for coordination between cerium isooctanoate and the polymeric superdispersant, and to determine the rheological stability of the slurry system by monitoring changes in dynamic viscosity, the following steps were taken:

[0107] 1) During the circulating grinding process of the horizontal closed sand mill, 50 ml slurry samples were taken from the discharge port at 0 minutes, 30 minutes, 60 minutes, 120 minutes and 240 minutes after the start of operation.

[0108] 2) Quickly seal the cut sample and place it in a 25°C constant temperature water bath for 15 minutes to eliminate the thermal effect and air bubbles caused by mechanical shearing.

[0109] 3) The dynamic viscosity of the sample was tested using a rotational rheometer. The test configuration used a coaxial cylindrical test system, and the rotor model was selected to match the standard rotor for medium and low viscosity fluids.

[0110] 4) Set the rheometer to a constant test temperature of 25℃ and the shear rate to 100s. -1 Record the values ​​displayed by the equipment system under steady-state shear. Measure the values ​​three times in parallel at each time point and record the average value.

[0111] Table 1. Changes in dynamic viscosity during the grinding process in Example 2 and Comparative Example 6

[0112] Grinding time (minutes) 0 30 60 120 240 Example 2: Dynamic viscosity (mPa·s) 142.6 118.3 91.5 87.2 84.8 Comparative Example 6: Dynamic viscosity (mPa·s) 155.1 298.4 631.7 1845.2 4102.5

[0113] in conclusion:

[0114] Figure 1 The solid line with a circular mark represents Example 2, and the dashed line with a square mark represents Comparative Example 6. This figure visually illustrates the differences in macroscopic rheological states between the two processes during the later stages of grinding. The viscosity curve of Example 2, after an initial slight decrease, remains stable at a low level, confirming the high stability of the steric hindrance layer constructed by the polymeric superdispersant under the stepwise feeding process; while the viscosity curve of Comparative Example 6 shows an exponential upward trend with a sudden increase in slope as the grinding time increases, eventually reaching a higher viscosity value, macroscopically exhibiting a systematic gelation phenomenon caused by severe agglomeration of inorganic nanoparticles.

[0115] Figure 2 The graph shows the same set of dynamic viscosity variation curves plotted on a semi-logarithmic ordinate. By converting the ordinate to a logarithmic scale, the graph effectively magnifies the detailed differences in rheological behavior between the two systems during the initial and intermediate stages of grinding. The semi-logarithmic curves clearly reveal that in Comparative Example 6, the failure of its internal microstructure within the first 60 minutes of grinding led to a logarithmic increase in fluid resistance, further confirming that the cerium ion competitive coordination reaction caused by incorrect feeding timing began to disrupt the stability of the dispersion system at a very early stage; it also more accurately reflects that Example 2 maintained excellent and constant Newtonian or near-Newtonian fluid characteristics even during a high-shear grinding cycle of up to 240 minutes.

[0116] According to the data in Table 1, the dynamic viscosity of the sample in Example 2 showed a trend of first decreasing and then stabilizing with increasing grinding time. At 0 minutes, the viscosity of the sample in Example 2 was 142.6 mPa·s, decreasing to 91.5 mPa·s after 60 minutes of grinding, and reaching 84.8 mPa·s after 240 minutes. The dynamic viscosity of the sample in Comparative Example 6 showed an increasing trend with increasing grinding time. At 0 minutes, the viscosity of the sample in Comparative Example 6 was 155.1 mPa·s, rising to 631.7 mPa·s after 60 minutes, and reaching 4102.5 mPa·s after 240 minutes, indicating severe gelation.

[0117] Example 2 employs a step-by-step feeding process. In the initial dispersion stage, the system contains only a mixed solvent, a polymeric superdispersant, and inorganic powder. The tertiary amine groups within the superdispersant molecular chains undergo hydrogen bonding and acid-base interactions with the surface of the cesium tungsten bronze powder, constructing a steric hindrance layer that prevents physical contact between the powder particles. Before the subsequent addition of cerium isooctanoate, the superdispersant has already coated the powder surface. The change in solvent polarity causes intermolecular entanglement between the aliphatic long chains within the cerium isooctanoate and the hydrophobic ends of the dispersant. Tetravalent cerium ions remain on the periphery of the Stern layer on the powder surface. This steric hindrance mechanism cuts off the physical path for contact between the tetravalent cerium ions and the tertiary amine groups of the dispersant.

[0118] Comparative Example 6 incorporated cerium isooctanoate in the initial grinding stage. The tetravalent cerium ions in the system possess strong coordination ability, preferentially coordinating with tertiary amine groups on the dispersant molecules under mechanical shear. This competitive coordination reaction causes the dispersant to detach from the powder surface. The cesium tungsten bronze nanoparticles, deprived of steric hindrance, re-aggregate under van der Waals forces. The increased volume of the micro-particle aggregates hinders relative slippage within the fluid, leading to a continuous increase in macroscopic dynamic viscosity and eventual gelation. The stepwise in-situ modification process avoids the competitive coordination reaction of cerium ions, ensuring the rheological stability of the nanoparticles within the coating system.

[0119] Test Example 2:

[0120] The effects of alkoxy-hindered amine light stabilizers on the curing crosslinking kinetics and crosslinking density of a two-component polyurethane system were verified through the following steps:

[0121] 1) Take component A prepared in Example 2 and Comparative Example 3, and add aliphatic hexamethylene diisocyanate trimer as component B according to the set molar ratio, and mix evenly by mechanical stirring for 5 minutes.

[0122] 2) Use a wire bar coater to evenly coat the mixed paint onto the surface of the degreased tinplate and polytetrafluoroethylene sheet, and control the dry film thickness to be 40 to 50 micrometers.

[0123] 3) Place the coated sample in a constant temperature and humidity chamber, set the temperature to 25℃ and the relative humidity to 50%, and cure at room temperature.

[0124] 4) At the 0, 1, 2, and 4-hour mark of the curing reaction, the coating on the polytetrafluoroethylene (PTFE) plate was scanned using an attenuated total reflectance Fourier transform infrared spectroscopy (ATIR) instrument, and the values ​​at 2270 cm⁻¹ were recorded. -1 The isocyanate group conversion rate is calculated by integrating the area of ​​the characteristic absorption peak of the isocyanate group (-NCO).

[0125] 5) After the coating has cured at room temperature for 7 days, peel off the free coating from the polytetrafluoroethylene plate and accurately weigh about 2.0 grams of the free film sample and wrap it in quantitative filter paper.

[0126] 6) Place the wrapped free membrane into a Soxhlet extractor and reflux extract with acetone as solvent for 24 hours.

[0127] 7) After extraction, remove the residue and dry it in an 80℃ vacuum drying oven until constant weight. Weigh and calculate the gel fraction.

[0128] Table 2. Test data on isocyanate group conversion rate and gel fraction during the coating curing reaction process of Example 2 and Comparative Example 3.

[0129] Test Project Test conditions Example 2 Data Comparative Example 3 Data Isocyanate group conversion rate (%) Curing for 1 hour 41.2 62.7 Isocyanate group conversion rate (%) Curing for 2 hours 73.8 81.5 Isocyanate group conversion rate (%) Curing for 4 hours 91.6 93.2 Gel fraction (%) Curing at room temperature for 7 days 96.4 71.2

[0130] in conclusion:

[0131] Figure 3 The graph shows the change in isocyanate group (-NCO) conversion rate over time in a two-component polyurethane system during the first 4 hours of room temperature curing. The solid line marked with a solid circle represents Example 2 (containing the alkoxy-hindered amine NOR-HALS), and the dashed line marked with a hollow square represents Comparative Example 3 (containing the conventional hindered amine HALS). As can be seen from the graph, the slope of the conversion rate curve in Comparative Example 3 is significantly greater than that in Example 2 during the initial reaction phase (0-2 hours). This indicates that the active secondary amine group in the conventional hindered amine preemptively undergoes a rapid nucleophilic addition reaction with the isocyanate group, leading to unintended consumption of the curing agent. In contrast, the curve in Example 2 exhibits standard step-growth polymerization kinetics, confirming that the alkoxy-hindered amine does not interfere with the normal curing reaction of the main chain.

[0132] Figure 4 A bar chart comparing gel fractions after 7 days of complete curing of the coating is presented. Dark bars represent Example 2, and light bars represent Comparative Example 3. The data shows that Example 2 achieved a gel fraction as high as 96.4%, indicating the formation of a well-developed and dense three-dimensional cross-linked network. In contrast, Comparative Example 3 only achieved a gel fraction of 71.2%, indicating a significant decrease in cross-linking density due to the end-capping effect of the hindered monofunctional amine, resulting in the presence of a large amount of unreacted oligomers or soluble components. This chart visually demonstrates the decisive influence of the selection of active components on the final physical structure of the coating.

[0133] According to the data in Table 2, there are differences between Example 2 and Comparative Example 3 in terms of curing crosslinking reaction kinetics and final crosslinking density. Regarding isocyanate group conversion, after 1 hour of curing, Comparative Example 3 had a conversion rate of 62.7%, higher than Example 2's 41.2%. Gel fraction testing after 7 days of curing showed that the coating of Example 2 had a gel fraction of 96.4%, with an intact crosslinked network structure; while Comparative Example 3 had a gel fraction of 71.2%, indicating the presence of uncrosslinked oligomers or soluble components.

[0134] In Example 2, the solid-phase oxidant precursor used was an alkoxy-hindered amine. The nitrogen atom of the piperidine ring in this compound is replaced by an alkoxy group, and the molecular structure does not contain active hydrogen atoms. During room-temperature curing, this compound is chemically inert to the isocyanate groups in component B. The isocyanate groups in the system only undergo stepwise addition polymerization with the hydroxyl groups of the hydroxyl acrylic resin in component A, forming urethane crosslinks and constructing a polyurethane crosslink network according to the expected kinetics.

[0135] Comparative Example 3 replaced the solid-phase oxidant precursor with a conventional hindered amine light stabilizer. The piperidine ring in the conventional hindered amine molecule contains a secondary amine group, which carries a highly reactive active hydrogen atom. In the initial stage of paint mixing, the nucleophilic addition reaction of the secondary amine group to the isocyanate group is more reactive than that of the hydroxyl group, consuming the curing agent in the system, resulting in a higher early isocyanate group conversion rate as detected by infrared spectroscopy. Some isocyanate groups are consumed by the monofunctional hindered amine molecule, forming urea bonds that end-cap, blocking the extension of the main chain and network crosslinking. The decreased crosslink node density leads to a lower gel fraction and increased soluble matter in the final paint film. Using an alkoxy-hindered amine avoids the competitive reaction with the curing agent, ensuring the crosslinking density of the two-component paint film.

[0136] Test Example 3:

[0137] The effects of nano-pigment dispersion level and active components on the initial thermal insulation performance of the coating were verified by evaluating the optical parameters of the cured coating in the visible and infrared light bands. The specific steps are as follows:

[0138] 1) Take the paint liquid of component A prepared in Examples 1 to 4 and Comparative Examples 1, 2, 4 and 5, mix it with component B in the set ratio, and use a 100-micron wire bar coater to form a film on a clean 3mm float glass surface.

[0139] 2) The sample was horizontally cured at 25°C for 24 hours to ensure that the coating was completely dry and free of dust contamination, and the dry film thickness was maintained at 35 to 40 micrometers.

[0140] 3) Turn on the UV-Vis-NIR spectrophotometer to perform baseline calibration, and set the scanning range to 380nm to 2500nm.

[0141] 4) Place the sample vertically in the measurement optical path, test the transmittance of the coating in the visible light band (380-780nm), and calculate the visible light transmittance (VLT) based on the standard integral.

[0142] 5) Record the near-infrared transmittance at 950nm and 1400nm, and calculate the near-infrared blocking rate (IRR) of the coating using a blank white glass of the same specification as a reference.

[0143] 6) The transmitted haze value of the sample was tested using a haze meter. Five measurement points were selected for each sample, including the center and the surrounding area. The average value was taken as the final optical data of the sample.

[0144] Table 3. Initial optical performance test data of the cured coatings in the examples and comparative examples

[0145] Sample number Visible light transmittance (VLT) (%) Near-infrared blocking rate at 950nm (%) Near-infrared blocking rate at 1400nm (%) Haze (%) Example 1 75.3 88.4 91.2 0.82 Example 2 73.1 92.7 94.5 0.91 Example 3 69.4 95.8 97.3 1.15 Example 4 74.2 90.6 93.4 0.88 Comparative Example 1 72.8 93.1 94.8 0.94 Comparative Example 2 73.5 92.4 94.2 0.87 Comparative Example 4 68.2 91.9 93.7 1.42 Comparative Example 5 71.6 84.5 87.1 2.56

[0146] in conclusion:

[0147] Figure 5 The figures show the spectral transmittance curves of the cured coatings of Example 2 and Comparative Example 5, reconstructed from measured data using a UV-Vis-NIR spectrophotometer, across the entire wavelength range from 380 nm to 2500 nm. The light gray background area in the figures represents the visible light region (380-780 nm). The solid line represents Example 2, the dashed line represents Comparative Example 5, and the black dots and squares correspond to the measured infrared transmittance (100% - near-infrared blocking rate) at 950 nm and 1400 nm, respectively, in Table 3. The curves in the figures show that Example 2 exhibits an extremely steep downward slope and a very deep absorption valley in the near-infrared region, with a transmittance as low as 7.3% at 950 nm. In contrast, Comparative Example 5, prepared using a one-pot method, shows a significantly shallower near-infrared absorption valley, with the transmittance at 1400 nm rising to 12.9%. This curve shape directly confirms that the mesoscopic dispersion state established by the stepwise anchoring process significantly increases the absorption cross-section of near-infrared photons by plasmon resonance on the surface of hexagonal cesium tungsten bronze nanoparticles.

[0148] Figure 6 This is a bar chart showing the transmission haze test data for all examples and comparative examples of cured coatings. The dashed line in the chart is the 1.2% reference baseline defining the high transparency standard of the coating. The dark gray bars represent the example group. The data shows that the haze of Examples 1, 2, and 4 is strictly controlled below 1.0%, even with Cs xExample 3, with a high WO3 solids content, did not exceed 1.2%, indicating that the nanoparticles were thoroughly pulverized without secondary agglomeration, and the Mie scattering effect was minimized. The light gray column on the right reveals the negative optical consequences of changing the process or medium: Comparative Example 4 (using ferric acetylacetone instead of cerium isooctanoate) experienced a haze increase to 1.42% due to the color development caused by iron ion impurities; Comparative Example 5, due to the lack of steric protection for nanoparticles caused by the one-pot process, experienced severe agglomeration, and its haze surged to 2.56%, completely losing its application value as an optical-grade transparent heat-insulating coating.

[0149] According to the data in Table 3, each embodiment achieved a balance between high visible light transmittance and high near-infrared blocking rate. In Example 2, based on a visible light transmittance of 73.1%, the near-infrared blocking rates at 950 nm and 1400 nm reached 92.7% and 94.5%, respectively, while the haze was controlled at a low level of 0.91%.

[0150] The optical performance of Examples 1 to 4 is consistent with that of cesium tungsten bronze (Cs). x WO3 exhibits strong absorption characteristics in the near-infrared region. With the development of Cs... x With the increase of WO3 content (from 5.0% in Example 1 to 8.0% in Example 3), the visible light transmittance decreased from 75.3% to 69.4%, while the infrared blocking performance was significantly improved. Due to the use of stepwise grinding and in-situ anchoring processes, the nano-pigment maintained excellent mesoscopic dispersion in the resin system. The powder particle size D50 was controlled between 40nm and 60nm, much smaller than the visible light wavelength, reducing Mie scattering and thus keeping the coating haze below 1.2%, ensuring the transparency of the coating.

[0151] Comparative Example 5, prepared using a one-pot method, showed a significantly lower near-infrared blocking rate (84.5% at 950 nm) than Example 2 with the same composition, and its haze increased to 2.56%. This indicates that nanoparticles without pre-dispersion and stepwise anchoring treatment are prone to secondary agglomeration during sand milling, resulting in a decrease in effective specific surface area, a reduction in the infrared absorption cross section, and enhanced scattering. Comparative Example 4, due to the introduction of ferric isooctanoate instead of cerium isooctanoate, suffered from a decrease in visible light transmittance to 68.2% due to the residual hue of iron ions, and exhibited a noticeable yellowish tint. The test results demonstrate that the modification process and component selection of this invention achieve uniform and stable dispersion of the nano-slurry without compromising initial optical properties, laying a physical foundation for the subsequent anti-photochromic function.

[0152] Test Example 4:

[0153] The efficacy of the cascade redox system constructed from cerium isooctanoate and alkoxy-hindered amine light stabilizer in suppressing the photochromic phenomenon of hexagonal cesium tungsten bronze nanoparticles was verified. The specific steps are as follows:

[0154] 1) Take the coated glass samples of Example 2 and Comparative Examples 1, 2, 4 and 5, which have been cured into films and whose initial optical parameters have been recorded, and prepare them into samples of standard test size.

[0155] 2) Place the sample in an accelerated aging test chamber equipped with a UVB-313 fluorescent ultraviolet lamp, with the coated surface of the sample facing the light source.

[0156] 3) Set the black panel temperature of the test chamber to 50℃, and the irradiance of the lamp at a wavelength of 310nm to 0.71W / m². 2 The equipment is turned on for continuous non-condensing ultraviolet irradiation.

[0157] 4) When the ultraviolet irradiation continues for 24 hours, 48 ​​hours, and 100 hours, stop the irradiation and remove the sample.

[0158] 5) Use a spectrophotometer and colorimeter to test the visible light transmittance and L*, a*, b* chromaticity coordinates of the irradiated sample block. After the test is completed, quickly put the sample block back into the test chamber to continue aging.

[0159] 6) Calculate the attenuation of transmittance relative to the initial value ΔVLT at each time point, and calculate the total color difference ΔE at each time point relative to the initial state according to the CIE1976 standard.

[0160] Table 4. Photochromic data of QUV accelerated aging test of coatings in Example 2 and comparative examples.

[0161] Sample number Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 4 Comparative Example 5 Transmittance attenuation ΔVLT (%) after 24 hours of irradiation 0.9 7.2 2.4 4.8 3.7 Color difference value ΔE after 24 hours of irradiation 0.5 4.6 1.8 4.1 3.2 Transmittance attenuation ΔVLT (%) after 48 hours of irradiation 1.6 13.8 8.6 9.5 10.4 Color difference value ΔE after 48 hours of irradiation 1.2 9.1 6.1 7.9 7.3 Transmittance attenuation ΔVLT (%) after 100 hours of irradiation 2.5 21.5 16.3 17.2 18.6 Color difference value ΔE after 100 hours of irradiation 1.7 15.2 12.8 14.4 14.9

[0162] in conclusion:

[0163] Figure 7 The graph shows the trend of visible light transmittance attenuation (ΔVLT) of each coating group over time during 100 hours of continuous ultraviolet irradiation. The flat solid line marked with a solid circle represents Example 2, whose ΔVLT value increases very little throughout the entire test period, decreasing by only 2.5% over 100 hours. This confirms that the cascade mediator system constructed by cerium ions and alkoxy-hindered amines can continuously and efficiently extract and consume photogenerated electrons from the powder surface, preventing electron accumulation within the crystal lattice. The dashed line representing Comparative Example 1 (cerium-deficient) exhibits the largest slope and peak value, with a linear drop in transmittance. The dotted line representing Comparative Example 2 (alkoxy-hindered amine-deficient) shows a relatively slow attenuation in the 0-24 hour range, but the slope increases sharply after cerium ions are depleted (starting from 48 hours), exhibiting typical hysteretic photochromic characteristics on the graph.

[0164] Figure 8The figure shows the trajectory of the total color difference (ΔE) of each coating group over time within the same aging cycle. The gray solid line crossing the coordinate system in the figure is the set visual tolerance reference line (ΔE=2.0). As can be seen from the figure, only the color difference curve of Example 2 is consistently suppressed below this critical line, with a final value of 1.7, which macroscopically indicates that the coating maintains a high degree of transparency and colorlessness for a long time. The curves of Comparative Example 4 (iron substitution) and Comparative Example 5 (one-pot method) both show a continuous divergent upward trend, with their 100-hour color difference values ​​exceeding 14.4 and 14.9, respectively. This sub-figure intuitively reflects the energy level matching of the transition metal medium and the spatial anchoring effect brought about by the dispersion modification process, which has a decisive influence on completely blocking the formation of polarons on the surface of nano-cesium tungsten bronze.

[0165] According to the data in Table 4, in Example 2, under 100 hours of high-intensity ultraviolet irradiation, the visible light transmittance decreased by only 2.5%, and the color difference value remained at a low level of 1.7. No obvious signs of blackening or bluening were observed in the coating to the naked eye. In contrast, Comparative Examples 1 to 5, after undergoing the same irradiation, showed a significant decrease in transmittance, severely exceeded the color difference value, and lost the transparent properties expected of the heat-insulating coating.

[0166] After absorbing ultraviolet light, hexagonal cesium tungsten bronze nanoparticles undergo valence band electron excitation and transition to the conduction band. Free electrons accumulate at lattice defects, causing hexavalent tungsten to be reduced to pentavalent tungsten and forming polarons. Macroscopically, this manifests as a broadening of the near-infrared absorption peak into the visible light region, resulting in a sharp drop in the transmittance of the coating film and a darkening of its color. Example 2 constructed a heterogeneous redox gradient layer composed of cerium isooctanoate and alkoxy-hindered amines. Tetravalent cerium ions, possessing a high electrode potential, preferentially capture photogenerated electrons on the surface of cesium tungsten bronze at the mesoscale, oxidizing them back to the hexavalent state and transforming themselves into trivalent cerium ions. The alkoxy-hindered amine, located on the periphery of the gradient layer, re-oxidizes trivalent cerium ions back to tetravalent cerium ions through a long-term free radical cyclic regeneration mechanism, completing the relay consumption and mediator regeneration of electrons. The solid-phase electron spin exchange channel remains unobstructed, preventing the accumulation of electrons within the inorganic powder.

[0167] Comparative Example 1, lacking cerium isooctanoate, prevented photogenerated electrons from crossing the phase interface, directly causing the cesium tungsten bronze to undergo reduction discoloration. Comparative Example 2, lacking alkoxy-hindered amine, saw tetravalent cerium ions, acting as sacrificial agents, absorb electrons initially and then transform into a lower valence state. However, the lack of a regeneration pathway led to the failure of the electron quenching mechanism after 24 hours, resulting in severe delayed discoloration of the coating. Comparative Example 4 used iron ions instead of cerium ions. The electron affinity of iron ions did not match the band structure of tungsten ions and easily induced photo-oxidative degradation of the resin matrix, leading to a significant increase in color difference. Comparative Example 5 used a one-pot mixing method, with the active material freely dispersed in the continuous resin phase. The redox mediator failed to form an effective anchoring and enrichment layer on the powder surface. The electron transfer path between the solid and liquid interfaces was too long, and steric hindrance hindered the collision probability, preventing the formation of an efficient cascade electron trapping effect. Ultimately, the anti-photochromic performance was far inferior to that of Example 2.

[0168] Test Example 5:

[0169] The specific steps for verifying the storage stability of coating component A under accelerated thermal aging conditions and the anti-agglomeration performance of the nano-dispersion system are as follows:

[0170] 1) Take 200g of each of the paint components A prepared in Examples 2, 4, Comparative Example 1 and Comparative Example 5, and put them into tin cans with a capacity of 250ml, and seal them with a can sealing machine.

[0171] 2) Turn on the rotational rheometer and dynamic light scattering particle size analyzer, set the test temperature to 25℃, measure the initial dynamic viscosity and median diameter D50 of each component sample before sealing, and record the test values.

[0172] 3) Place the sealed tin can in a constant temperature drying oven, set the ambient temperature inside the oven to 50℃, and leave it for 30 consecutive days to conduct a thermal storage accelerated aging test.

[0173] 4) After 30 days, remove the tin can and let it cool in a 25°C indoor environment for 24 hours until the sample center temperature reaches room temperature.

[0174] 5) Open the iron can, use a glass rod to check the sedimentation at the bottom, repeat step 2, and measure the dynamic viscosity and median diameter D50 of the sample after thermal aging.

[0175] 6) Compare the initial values ​​with the values ​​after aging, and calculate the growth rate of dynamic viscosity and the growth rate of median diameter for each sample.

[0176] Table 5. Rheological and particle size test data before and after thermal accelerated aging in the examples and comparative examples.

[0177] Sample number Initial dynamic viscosity (mPa·s) Dynamic viscosity after aging (mPa·s) Viscosity growth rate (%) Initial median diameter D50 (nm) Median diameter D50 (nm) after aging Particle size growth rate (%) Example 2 121.4 129.8 6.9 51.7 54.2 4.8 Example 4 118.6 127.3 7.3 48.3 51.1 5.8 Comparative Example 1 125.2 141.5 13.0 50.8 56.4 11.0 Comparative Example 5 146.2 415.7 184.3 58.4 132.9 127.6

[0178] in conclusion:

[0179] Figure 9 The changes in macroscopic dynamic viscosity of component A of each coating group before and after accelerated aging at a constant temperature of 50°C for 30 days are shown. In the figure, light gray bars represent the initial dynamic viscosity before aging, and dark gray bars represent the dynamic viscosity after aging. In Examples 2 and 4, the dynamic viscosity remained stable after thermal aging, with minimal changes in the height of the bars and a viscosity growth rate controlled within 8%, confirming that the polymeric superdispersant in the system was firmly anchored and effectively maintained the rheological equilibrium of the dispersed phase. In Comparative Example 5, the viscosity bar height increased dramatically after aging, rising sharply from 146.2 mPa·s to 415.7 mPa·s, reflecting the severe internal relative slip resistance and macroscopic gelation tendency caused by the competitive coordination reaction of metal ions introduced by the one-pot method.

[0180] Figure 10 The figure shows the change in the median diameter (D50) of the mesoscopic particles before and after aging of the corresponding samples. This figure confirms the root cause of the deterioration of macroscopic rheological properties through microscopic particle size. The dark gray and light gray pillars in Examples 2 and 4 are similar in height, and their median diameter remains below 55 nm after aging, indicating that the steric hindrance layer on the surface of the nanoparticles successfully resisted Brownian thermal collisions at 50°C, preventing particle agglomeration. The median diameter of Comparative Example 5 increased sharply to 132.9 nm after aging, with a particle size growth rate as high as 127.6%, which intuitively reveals the failure of the protective layer caused by the desorption of the superdispersant, resulting in irreversible secondary aggregation of the exposed cesium tungsten bronze nanoparticles under the action of van der Waals attraction.

[0181] According to the data in Table 5, after 30 days of accelerated thermal aging at 50°C, Examples 2 and 4 showed relatively small increases in dynamic viscosity and median diameter. Example 2 had an initial dynamic viscosity of 121.4 mPa·s, which increased to 129.8 mPa·s after aging; the initial median diameter (D50) was 51.7 nm, which increased to 54.2 nm after aging. Comparative Example 5, after undergoing the same thermal aging process, showed deterioration in rheological and particle size parameters. Comparative Example 5 had an initial dynamic viscosity of 146.2 mPa·s, which increased to 415.7 mPa·s after aging, representing a viscosity increase of 184.3%; the initial median diameter was 58.4 nm, which increased to 132.9 nm after aging, representing a particle size increase of 127.6%.

[0182] This embodiment employs a stepwise in-situ anchoring process to prepare nano-color pastes. The tertiary amine groups of the polymeric superdispersant form hydrogen bonds and acid-base anchoring with the surface of cesium tungsten bronze powder, while the polymeric chain segments construct a steric hindrance layer around the powder. The added cerium isooctanoate and its alkoxy-hindered amine complex undergo van der Waals entanglement with the hydrophobic tail of the superdispersant at the mesoscale. The active component does not encroach on the adsorption sites of the superdispersant on the inorganic powder surface. The nanoparticles maintain the interparticle repulsive barrier. In a 50°C thermal environment, Brownian motion does not overcome the interparticle repulsion, and the slurry system maintains its original dispersion state.

[0183] Comparative Example 5 employed a one-pot mixing process. Transition metal ions within cerium isooctanoate, under shear force, intervened in the adsorption process at the interface between the inorganic powder and the dispersant. These metal ions occupied the active sites on the surface of cesium tungsten bronze, blocking the anchoring of the tertiary amine groups in the dispersant. Desorption of the superdispersant led to a reduction in the steric hindrance layer thickness on the powder surface, exposing the particle surface. The kinetic energy provided by the thermal storage environment induced collisions between the metastable nanoparticles. The steric hindrance-free cesium tungsten bronze particles aggregated under van der Waals attraction, resulting in a doubling of the median diameter. The solvent was encapsulated within the voids of the micro-aggregates, leading to a decrease in the free solvent volume fraction within the continuous phase, increased fluid flow resistance, and a macroscopic increase in dynamic viscosity. The stepwise process established the hierarchical distribution of the dispersant and active materials, maintaining the shelf life of the coating system.

Claims

1. A glass reflective heat-insulating paint, characterized in that, Includes component A and component B; The components of component A, by mass percentage, include: Solvent-based hydroxyl acrylic resin: 45.0%-55.0%; Hexagonal cesium tungsten bronze nanoparticles: 5.0%-8.0%; Anchored polymeric superdispersant: 1.0%-2.5%; Cerium isooctanoate: 0.2%-0.6%; bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidinyl) sebacate: 0.8%-1.5%; Leveling agent: 0.1%-0.3%; Mixed solvent: balance, bring to 100%; Component B is an aliphatic hexamethylene diisocyanate trimer; The molar ratio of the hydroxyl groups of the solvent-based hydroxyl acrylic resin in component A to the isocyanate groups of the aliphatic hexamethylene diisocyanate trimer in component B is 1:1.05-1:1.

15.

2. The glass reflective heat-insulating paint according to claim 1, characterized in that, The anchoring polymeric superdispersant is an acrylate block copolymer containing tertiary amine anchoring groups. The polymeric monomers of the anchoring polymeric superdispersant include at least methyl methacrylate, butyl acrylate, and N,N-dimethylaminoethyl methacrylate. The tertiary amine groups of the anchoring polymeric superdispersant form hydrogen bonds with the surface of the hexagonal cesium tungsten bronze nanoparticles for acid-base anchoring.

3. The glass reflective heat-insulating paint according to claim 1, characterized in that, The mixed solvent is a mixture of propylene glycol methyl ether acetate and butyl acetate in a mass ratio of 0.8:1 to 1.2:1; The solvent-based hydroxyl acrylic resin has a solid content of 65%-75% and a hydroxyl mass fraction of 2.5%-3.5%. The cerium mass fraction in the cerium isooctanoate is 10%-12%; The leveling agent is polyether-modified polydimethylsiloxane.

4. The glass reflective heat-insulating paint according to claim 1, characterized in that, In component A, the surface of the hexagonal cesium tungsten bronze nanoparticles is coated with the anchoring polymeric superdispersant, and the cerium isooctanoate and the sebacic acid bis(1-octoxy-2,2,6,6-tetramethyl-4-piperidinyl) ester are distributed and bound to the hydrophobic tail of the anchoring polymeric superdispersant.

5. The glass reflective heat-insulating paint according to claim 1, characterized in that, The mass ratio of cerium isooctanoate to sebacic acid bis(1-octoxy-2,2,6,6-tetramethyl-4-piperidinyl) ester is 1:2.5-1:4.

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6. The glass reflective heat-insulating paint according to claim 3, characterized in that, The glass reflective heat-insulating paint is prepared by the following steps: After the mixed solvent and the anchored polymeric superdispersant are mixed evenly, the hexagonal crystal system nano-cesium tungsten bronze powder is added and dispersed by high-speed shearing. Then, it is pumped into a horizontal closed sand mill for circulating grinding until the D50 particle size of the slurry reaches 40nm-60nm to obtain nano-color paste. Cerium isooctanoate and sebacic acid bis(1-octoxy-2,2,6,6-tetramethyl-4-piperidinyl) ester are not added at this stage. The nano-color paste was transferred to the reaction vessel and the stirring speed was adjusted to 300 rpm-500 rpm; The cerium isooctanoate and the sebacic acid bis(1-octoxy-2,2,6,6-tetramethyl-4-piperidinyl) ester were pre-mixed in propylene glycol methyl ether acetate to form a complex solution; The complexing solution was added to the nano-color paste in the reactor at a dropping rate of 1.0 kg / min-2.0 kg / min, the temperature inside the reactor was controlled at 30℃-40℃, and the mixture was stirred continuously for 1.5-2.0 hours to obtain the modified slurry. The solvent-based hydroxyl acrylic resin was added to the paint mixing tank before stirring, and then the modified slurry was slowly added dropwise, along with the leveling agent. The mixture was stirred and filtered to obtain component A. The A component and the aliphatic hexamethylene diisocyanate trimer, which is the B component, are used together to form the two-component glass reflective heat-insulating paint.

7. The glass reflective heat-insulating paint according to claim 6, characterized in that, The specific process parameters for obtaining the nano-color paste are as follows: Add the mixed solvent and the anchored polymeric superdispersant to the mixing tank and stir for 15-20 minutes at a speed of 500rpm-800rpm. The hexagonal cesium tungsten bronze nanoparticles are added in batches at a uniform speed, and the rotation speed is increased to 1500rpm-2000rpm for high-speed dispersion for 45-60 minutes. The horizontal closed sand mill is filled with 0.1mm-0.3mm zirconia beads, the temperature of the grinding liquid is controlled at 25℃-35℃, the linear speed of the grinding rotor is set at 10m / s-12m / s, and the grinding is circulated for 3-5 hours.

8. The glass reflective heat-insulating paint according to claim 2, characterized in that, The specific synthesis steps of the anchored polymeric superdispersant include: Heat 30.0 parts by weight of propylene glycol methyl ether acetate to 90℃-95℃; A monomer mixture was prepared by mixing 40.0 parts by weight of methyl methacrylate, 20.0 parts by weight of butyl acrylate, 10.0 parts by weight of N,N-dimethylaminoethyl methacrylate and 1.5 parts by weight of azobisisobutyronitrile. At a constant temperature of 90℃-95℃, the monomer mixture was added dropwise to the propylene glycol methyl ether acetate at a constant rate for 3.0-3.5 hours. After the reaction is kept at a constant temperature for 0.8-1.5 hours, add 0.2 parts by weight of azobisisobutyronitrile dissolved in propylene glycol methyl ether acetate, continue to keep at a constant temperature for 1.5-2.5 hours, cool down to below 40°C, and filter out the material.

9. The glass reflective heat-insulating paint according to claim 6, characterized in that, After adding the solvent-based hydroxyl acrylic resin to the paint mixing tank, the stirring speed is 600rpm-800rpm. The modified slurry and the leveling agent are slowly added dropwise, and the stirring time is continued for 30-45 minutes.

10. A glass reflective heat-insulating paint according to claim 6, characterized in that, The prepared component A and the aliphatic hexamethylene diisocyanate trimer, which is component B, are separately sealed and packaged. Before use at the terminal, mix component A with component B.

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