Preparation method of reflective heat-insulation waterproof real stone paint

Abstract

The invention belongs to the technical field of building materials, and discloses a preparation method of reflective heat-insulation waterproof real stone paint, which comprises the following three process stages: core layer synthesis, shell layer loading and real stone paint integration: coating a continuous SiO layer on the surface of nano TiO in situ to form TiO-coated SiO particles; graphene quantum dots and a hindered amine light stabilizer are loaded on the surfaces of TiOatSiO particles to form a composite functional filler; adding the composite functional filler into the acrylic emulsion base material in batches at a low speed, and adjusting the rheological property with the aid to obtain a finished product. The preparation process disclosed by the invention is completely compatible with an existing real stone paint industrial production line, does not need to add special equipment, and has excellent reflective heat insulation, heat preservation, water resistance, weather resistance and aging resistance and large-scale industrial feasibility; the technical problems of resin oxidative degradation caused by TiO photocatalytic activity, rapid attenuation of solar radiation reflectivity, failure of waterproof and hydrophobic performance and easiness in damage and stripping of a coating structure of the existing nano TiO-based reflective heat-insulation real stone paint are solved.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to a method for preparing a reflective, heat-insulating, waterproof, and stone-like paint. Background Technology

[0002] Reflective thermal insulation coatings for building exterior walls have become core functional materials for reducing building air conditioning energy consumption and mitigating the urban heat island effect, and have achieved large-scale engineering applications. Among them, reflective thermal insulation stone paint with nano-TiO2 (TiO2) as the core functional filler has become the preferred material for the exterior wall cladding of high-end commercial buildings and landmark buildings due to its high solar radiation reflectivity (initial value ≥90%), decorative texture that simulates natural stone, good construction adaptability, and environmental friendliness.

[0003] However, in practical engineering applications, the inherent strong ultraviolet photocatalytic activity of TiO2 can induce irreversible chain oxidation degradation reactions under long-term solar irradiation, limiting the service life of such materials. The "White Paper on the Durability of Building Reflective Thermal Insulation Coatings" published by the China Academy of Building Research in 2022 states that conventional TiO2-based stone paints show significant performance degradation after 36 months of natural exposure. After 1000 hours of QUV accelerated aging, the solar radiation reflectivity attenuation rate generally exceeds 25%, far exceeding the 15% upper limit specified in the industry standard JC / T 1040-2021. The oxidative degradation of the resin also leads to a sharp increase in the surface energy of the coating, with the static water contact angle dropping from the initial 110° to below 80°. This causes the hydrophobic and waterproof barrier to fail, leading to water penetration, freeze-thaw cycle damage, and ultimately large-area peeling of the coating. This creates a technical paradox of "high reflectivity, short lifespan, and easy failure," which cannot meet the long-term service requirements of 10 or even 20 years for building exterior wall coatings.

[0004] To address the aforementioned issues, existing technologies have proposed several improvement schemes. One method involves a physical isolation approach using a single layer of SiO2 coated with TiO2. However, this coating layer is only 5-10 nm thick, resulting in low mechanical strength. High-shear stirring during coating preparation easily induces microcracks in the coating layer, making carrier escape unavoidable. Even after 500 hours of QUV aging, the reflectivity still decreases by 18.7%. Furthermore, the poor compatibility between SiO2 and the resin interface leads to low coating adhesion. Another method involves directly adding hindered amine light stabilizers for free radical capture. However, these small-molecule stabilizers have a migration rate exceeding 40% in the resin, easily forming internal protective voids. Direct contact between the stabilizer and TiO2 triggers esterification side reactions, accelerating resin degradation. After aging, the water contact angle is only 92°, and the waterproof function is on the verge of failure. A third method uses TiO2 / graphene composite fillers. However, graphene has a zeta potential of only -15 mV in the emulsion, resulting in poor dispersibility and easy aggregation. Its high conductivity accelerates electron-hole recombination, failing to quench reactive oxygen species and instead exacerbating localized aging.

[0005] In summary, existing improvement solutions are all optimizations of single steps and cannot form a systematic anti-aging protection system. There is an urgent need in this field to develop a preparation method that can reconstruct the interface structure between TiO2 and the resin matrix at the molecular scale, completely suppressing its negative photocatalytic effects while retaining the high reflectivity of TiO2, and taking into account the coating's reflective heat insulation, waterproofing, weather resistance, stability, and structural integrity, while also being compatible with existing industrial production processes. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing reflective, heat-insulating, waterproof, and real stone paint, in order to solve the problems of long molding time, non-reusability, and non-recyclability of forged textured materials during production.

[0007] This invention provides a method for preparing a reflective, heat-insulating, waterproof, and water-resistant stone-like paint, comprising the following steps: S1. Disperse nano-TiO2 particles in anhydrous ethanol to form a TiO2 dispersion. Adjust the pH of the dispersion to 9.5-10. Under constant temperature conditions, add tetraethyl orthosilicate solution dropwise to the dispersion. After the addition is complete, continue stirring to react and generate a SiO2 coating layer on the surface of the TiO2 particles. After the reaction is complete, centrifuge, wash and dry to obtain TiO2@SiO2 particles. S2. TiO2@SiO2 particles are dispersed in deionized water to form TiO2@SiO2 dispersion. After ultrasonic treatment, the dispersion is heated. Graphene quantum dots are added first under stirring. After stirring and dispersing, hindered amine light stabilizer is added. After the reaction is completed by stirring at a constant temperature, the mixture is centrifuged, washed and dried to obtain composite functional filler. S3. The acrylic copolymer emulsion and natural colored sand filler are placed in a mixing tank and sheared and dispersed to form a mixed base material. Under stirring conditions, the composite functional filler is added in three equal amounts in three batches. The total amount of composite functional filler added is 8-10 wt% of the mixed base material. After the addition is completed, stirring is continued. Then, defoamer and thickener are added and stirring is continued to obtain reflective heat insulation and waterproof stone paint.

[0008] Furthermore, in step S1, the TiO2 particle size is 50-80 nm, and the TiO2 concentration in the TiO2 dispersion is 5-10 wt%.

[0009] Furthermore, in step S1, the reaction temperature is 40–50°C, the dropping rate is 1–2 ml / min, and the molar ratio of TiO2 to tetraethyl orthosilicate is 1:0.5–0.6.

[0010] Furthermore, in step S2, the concentration of the TiO2@SiO2 dispersion is 3-3.5 wt%, the ultrasonic treatment frequency is 300-500 W, and the ultrasonic treatment time is 10-20 min.

[0011] Furthermore, in step S2, the final concentration of graphene quantum dots added is 0.18–0.22 wt%, and the final concentration of light stabilizer added is 0.14–0.16 wt%; the constant temperature stirring temperature is 60–65 °C, and the stirring time is 30–60 min.

[0012] Furthermore, in step S3, the particle size of the natural colored sand filler is 80-120 mesh, the addition amount is 12-18% of the mass of the acrylic copolymer emulsion, and the shear dispersion speed is 150-200 rpm; when adding the composite functional filler, the stirring speed is 150-200 rpm.

[0013] Furthermore, in step S3, the amount of defoamer added is 0.4-0.6 wt%, and the amount of thickener added is 0.2-0.4 wt%.

[0014] Beneficial effects: The finished product prepared by this invention has an initial solar radiation reflectance of 93.2%, far exceeding the performance requirements of reflective heat-insulating coatings. After 1000 hours of QUV accelerated aging, the reflectance remains at 86.5%, with a decay rate of only 7.2%, far below the specified upper limit of 15%. Simultaneously, the initial static water contact angle of the finished product is 112°, which is a high hydrophobicity level. After aging and thermal cycling, the water contact angle remains at 106°, effectively blocking moisture penetration and solving the problems of freeze-thaw damage, powdering, and peeling caused by water absorption in the coating.

[0015] The preparation process of this invention is fully compatible with existing industrial production lines for stone-like paint, requiring no additional specialized equipment; only adjustments to the feeding sequence and temperature control parameters are needed. Raw material costs are only 3.2% higher than conventional stone-like paint, resulting in a significantly higher overall cost-effectiveness compared to existing modified products, facilitating large-scale application. The finished product combines five major functions: high reflectivity for heat insulation, thermal insulation, long-lasting waterproofing, excellent weather resistance, and simulated stone decoration. No multi-layer application is required; a single spray coat is sufficient to meet the energy-saving and decorative needs of building exteriors, simplifying construction procedures and reducing costs. Detailed Implementation

[0016] The technical solution of the present invention will be described in detail below with reference to embodiments and comparative examples.

[0017] Unless otherwise specified, all raw materials described in this invention are commercially available.

[0018] This invention provides a method for preparing a reflective, heat-insulating, waterproof, and water-resistant stone-like paint, comprising the following steps: S1. Disperse nano-TiO2 particles in anhydrous ethanol to form a TiO2 dispersion. Adjust the pH of the dispersion to 9.5-10. Under constant temperature conditions, add tetraethyl orthosilicate solution dropwise to the dispersion. After the addition is complete, continue stirring to react and generate a SiO2 coating layer on the surface of the TiO2 particles. After the reaction is complete, centrifuge, wash and dry to obtain TiO2@SiO2 particles. Specifically, anatase-type nano-titanium dioxide particles with a particle size of 50–80 nm were dispersed in anhydrous ethanol and stirred until a uniform suspension was formed, preparing a 5 wt% TiO2 dispersion. Ammonia solution with a concentration of 0.1–0.2 mol / L was slowly added dropwise to the dispersion to adjust the pH to 9.5–10. The adjusted dispersion was placed in a constant-temperature water bath reactor and heated to 40°C. Tetraethyl orthosilicate (TEOS) solution was added dropwise at a constant rate of 1 mL / min, strictly controlling the molar ratio of nano-titanium dioxide to tetraethyl orthosilicate to be 1:0.5–0.6. After the addition was complete, the temperature was maintained at 40°C, and the reaction was continuously stirred for 2 hours, allowing the tetraethyl orthosilicate to undergo hydrolysis and condensation under alkaline catalysis, resulting in the in-situ formation of a 15–20 nm thick silica coating layer on the surface of the TiO2 particles.

[0019] After the reaction was complete, the resulting slurry was transferred to a high-speed centrifuge and centrifuged at 8000 rpm for 10 minutes, discarding the supernatant. The centrifuged precipitate was washed three times with anhydrous ethanol, centrifuged after each wash to thoroughly remove unreacted silicon sources, byproducts, and free ions. The washed precipitate was placed in a vacuum drying oven and dried at a constant temperature of 60°C for 12 hours. After cooling to room temperature, TiO2@SiO2 particles were obtained.

[0020] S2. TiO2@SiO2 particles are dispersed in deionized water to form TiO2@SiO2 dispersion. After ultrasonic treatment, the dispersion is heated. Graphene quantum dots are added first under stirring. After stirring and dispersing, hindered amine light stabilizer is added. After the reaction is completed by stirring at a constant temperature, the mixture is centrifuged, washed and dried to obtain composite functional filler. Specifically, the TiO2@SiO2 particles obtained above were dispersed in deionized water and stirred until uniformly dispersed to prepare a dispersion with a mass concentration of 3 wt%. This dispersion was placed in an ultrasonic disperser and ultrasonically treated for 10 minutes at a constant ultrasonic power of 300–500 W. During ultrasonication, an ice bath was used to control the temperature and prevent the system temperature from exceeding 30°C, ensuring complete deagglomeration of the TiO2@SiO2 particles and activation of the silanol groups on the surface of the SiO2 layer. The ultrasonically treated dispersion was then transferred to a constant-temperature water bath stirred tank, heated to 60°C, and stirred at a uniform speed.

[0021] Graphene quantum dots (GQDs) were added to the system, with the final concentration of GQDs controlled at 0.18–0.22 wt%, and the mixture was stirred at a constant temperature for 15 minutes. Then, hindered amine light stabilizers (HALS) were added to the system, with the final concentration controlled at 0.14–0.16 wt%. The system was maintained at a constant temperature of 60 °C, and stirring continued until the total stirring time reached 30 minutes, completing the molecular self-assembly reaction.

[0022] After the reaction was completed, the resulting slurry was transferred to a centrifuge and centrifuged at 6000 rpm for 10 minutes, and the supernatant was discarded. The centrifuged precipitate was washed twice with deionized water, and unbound graphene quantum dots and hindered amine light stabilizers were removed after centrifugation. The washed precipitate was placed in a forced-air drying oven and dried at a constant temperature of 50°C for 12 hours. After cooling to room temperature, the composite functional filler was obtained.

[0023] S3. The acrylic copolymer emulsion and natural colored sand filler are placed in a mixing tank and sheared and dispersed to form a mixed base material. Under stirring conditions, the composite functional filler is added in three equal amounts in three batches. The total amount of composite functional filler added is 8-10 wt% of the mixed base material. After the addition is completed, stirring is continued. Then, defoamer and thickener are added and stirring is continued to obtain reflective heat insulation and waterproof stone paint.

[0024] Specifically, the acrylic emulsion base material is placed in a jacketed, temperature-controlled stainless steel stirred tank. The acrylic emulsion base material is a fixed formula containing an acrylic copolymer emulsion with a solid content of 45% and a glass transition temperature (Tg) of 10°C, and 12-18 wt% of natural colored sand filler. The particle size distribution of the natural colored sand filler is 80-120 mesh, and its main component is quartz.

[0025] Start the stirring tank and adjust the stirring speed to a low-speed shearing state of 150-200 rpm. This speed is the core process parameter, which can avoid high-speed shearing from damaging the core-shell structure of the composite functional filler. Add the core-shell structure composite functional filler prepared above to the acrylic emulsion base in three equal amounts, according to the total addition amount of 8-10 wt%. The interval between two adjacent additions is 5 minutes to ensure that the filler is fully wetted and dispersed after each addition.

[0026] After the materials are added, maintain a low stirring speed of 150–200 rpm and continue stirring for 15 minutes to ensure that the composite functional filler is microscopically and uniformly dispersed in the emulsion base without damage to the core-shell structure. Then, add 0.4–0.6 wt% of an organosilicon defoamer and 0.2–0.4 wt% of an alkali-swellable thickener to the system sequentially, and continue stirring at low speed for 5 minutes to fully dissolve the additives and adjust the rheological properties of the system. After stirring is complete, stop the machine and filter through a 200-mesh filter to obtain the final reflective, heat-insulating, waterproof, and durable stone-like paint product. Example

[0027] 1 kg of anatase-type nano-TiO2 was dispersed in 19 kg of anhydrous ethanol and stirred for 30 min to obtain a 5 wt% dispersion. The pH was adjusted to 9.5 with 0.1 mol / L ammonia solution, and the mixture was transferred to a 40℃ constant-temperature reactor. TEOS solution was added dropwise at a molar ratio of TiO2:TEOS = 1:0.6 at a dropping rate of 1 mL / min. After the addition was complete, the mixture was stirred for 2 h. The mixture was centrifuged at 8000 rpm for 10 min, washed three times with anhydrous ethanol, dried under vacuum at 60℃ for 12 h, and passed through a 200-mesh sieve to obtain TiO2@SiO2 particles.

[0028] 0.5 kg of TiO2@SiO2 particles were dispersed in 15.1 kg of deionized water to obtain a 3.2 wt% dispersion. The dispersion was ultrasonicated at 300 W for 10 min (temperature controlled in an ice bath), then heated to 60 °C. 0.041 kg of GQDs (final concentration 0.20 wt%) was added, and the mixture was stirred for 15 min. Then, 0.031 kg of HALS (final concentration 0.15 wt%) was added, and the mixture was stirred for a total of 30 min. The mixture was centrifuged at 6000 rpm for 10 min, washed twice with deionized water, dried at 50 °C for 12 h, and passed through a 300-mesh sieve to obtain the composite functional filler.

[0029] Take 10 kg of acrylic emulsion base material and place it in a mixing tank. Stir at a low speed of 200 rpm. Add 0.9 kg of composite functional filler in three equal portions, with an interval of 5 minutes between each addition. Stir for 15 minutes after each addition. Add 0.05 kg of silicone defoamer and 0.03 kg of alkali-swelling thickener, stir for 5 minutes, and filter to obtain the finished reflective heat-insulating and waterproof stone paint.

[0030] The prepared stone-like paint underwent performance testing, and its solar radiation reflectance reached 93.2% (GB / T 23456-2023), with a contact angle of 112° (GB / T 30693-2014). After aging testing (GB / T 1865-2009), the solar radiation reflectance was 86.5%, and the contact angle was 106°.

Claims

1. A method for preparing a reflective, heat-insulating, waterproof, and natural stone-like paint, characterized in that: The method comprises the following steps: S1, dispersing nano-TiO2 particles in anhydrous ethanol to form a TiO2 dispersion, adjusting the pH value of the dispersion to 9.5-10, under constant temperature conditions, adding a tetraethyl orthosilicate solution dropwise to the dispersion, continuously stirring after the dropwise addition is completed to generate a SiO2 coating layer on the surface of the TiO2 particles, and after the reaction is completed, centrifuging, washing and drying to obtain TiO2@SiO2 particles; S2, dispersing the TiO2@SiO2 particles in deionized water to form a TiO2@SiO2 dispersion, ultrasonic treatment, heating the dispersion, and under stirring, first adding graphene quantum dots, stirring and dispersing, and then adding a hindered amine light stabilizer, maintaining constant temperature and stirring until the reaction is completed, and then centrifuging, washing and drying to obtain a composite functional filler; S3, placing an acrylic copolymer emulsion and a natural colored sand filler in a stirring kettle to shear and disperse to form a mixed base, under stirring, adding the composite functional filler in three equal portions, and the total amount of the composite functional filler is 8-10 wt% of the mixed base; after the addition is completed, continuing to stir, then adding a defoaming agent and a thickening agent, and continuing to stir to obtain a reflective, heat-insulating, heat-preservation, waterproof and true stone paint.

2. The preparation method of the reflective thermal insulation waterproof real stone paint according to claim 1, characterized in that: In the step S1, the TiO2 particle size is 50-80 nm, and the TiO2 concentration in the TiO2 dispersion is 5-10 wt%.

3. The preparation method of the reflective thermal insulation waterproof real stone paint according to claim 2, characterized in that: In the step S1, the reaction temperature is 40-50°C, the dropwise addition speed is 1-2 ml / min, and the molar ratio of TiO2 to tetraethyl orthosilicate is 1:0.5-0.

6.

4. The preparation method of the reflective thermal insulation waterproof real stone paint according to claim 1, characterized in that: In the step S2, the concentration of the TiO2@SiO2 dispersion is 3-3.5 wt%, the ultrasonic treatment frequency is 300-500 w, and the ultrasonic treatment time is 10-20 min.

5. The preparation method of the reflective thermal insulation waterproof real stone paint according to claim 4, characterized in that: In the step S2, the final concentration of the graphene quantum dots is 0.18-0.22 wt%, the final concentration of the light stabilizer is 0.14-0.16 wt%, the constant temperature stirring temperature is 60-65°C, and the stirring time is 30-60 min.

6. The preparation method of the reflective thermal insulation waterproof real stone paint according to claim 1, characterized in that: In the step S3, the particle size of the natural colored sand filler is 80-120 mesh, the amount of addition is 12-18% of the mass of the acrylic copolymer emulsion, the shear dispersion rotation speed is 150-200 rpm, and the stirring speed during the addition of the composite functional filler is 150-200 rpm.

7. The preparation method of the reflective thermal insulation waterproof real stone paint according to claim 6, characterized in that: In the step S3, the amount of addition of the defoaming agent is 0.4-0.6 wt%, and the amount of addition of the thickening agent is 0.2-0.4 wt%.