Preparation method of efficient radiation refrigeration coating

Abstract

The invention relates to the technical field of inorganic functional coatings, and discloses a preparation method of a high-efficiency radiation refrigeration coating, which is characterized by comprising the following steps: step 1, preparing a premixed solution from deionized water, an anti-mildew antibacterial agent, a wetting dispersant and a defoaming agent; 2, CaSO3 radiation refrigeration filler, lead-free functional filler and modified heat reflection TiO2 (rutile type) are sequentially added into the premixed liquid; step 3, grinding the dispersed slurry; step 4, adding SiO2 aerogel nanosheets, a single-component fluorosilicone emulsion, a water-based acrylic emulsion, a coalescing agent, a flatting agent, a thickening agent and a mildew-proof antibacterial agent; step 5, filtering; and 6, adding a pH regulator to regulate the pH of the system. Through the lattice doping effect of the calcium sulfite and the rare earth oxide, synergistic enhancement of sunlight full-band reflection and atmospheric window infrared emission is achieved, and the heat dissipation material is especially suitable for surface heat dissipation of high-humidity coastal area buildings and offshore equipment.

Description

Technical Field

[0001] The invention relates to the technical field of inorganic functional coatings, and in particular to a method for preparing a high-efficiency radiation refrigeration coating. Background Art

[0002] With the acceleration of urbanization, the various problems caused by the urban heat island effect have triggered a huge demand for cooling technologies and materials. However, traditional cooling technologies (such as air conditioning) consume approximately 10% of the world's electricity and further exacerbate greenhouse gas emissions. Therefore, there is an urgent need for low-energy cooling technologies. Daytime radiative cooling is a passive cooling technology that uses outer space as a cold sink, emitting heat through an "atmospheric window" while reflecting sunlight to avoid energy absorption. It can achieve significant sub-ambient cooling (i.e., below ambient temperature) without consuming any energy. Daytime radiative cooling coatings, due to their mature production process and controllable production costs, are considered one of the key materials for large-scale preparation and application. To achieve long-term and efficient cooling, daytime radiative cooling coatings must meet two basic requirements: first, high radiative cooling power (i.e., high solar reflectivity and mid- and far-infrared emissivity); second, long-term and stable weather resistance (such as resistance to UV aging, stain resistance, and water resistance). Rainwater is a significant factor affecting the performance of daytime radiant cooling coatings. Rainwater impact can damage the coating's mechanical properties. Combined with other natural factors, it can accelerate coating aging, yellowing, and even peeling from the substrate, leading to coating failure. However, research on rainwater resistance in daytime radiant cooling coatings is currently lacking.

[0003] Traditional fillers have the following limitations:

[0004] CaCO₃ has high reflectivity but is easily deliquescent (reflectivity decreases by 20% when humidity exceeds 70%). It absorbs moisture in humid environments, causing it to lose its hardness and strength. ZnO, while weather-resistant, has a narrow infrared emission band (emissivity <85% in the 8-10 μm range) and is relatively expensive compared to other traditional materials, hindering widespread adoption. Traditional radiative cooling coatings use SrSO₄ to improve weather resistance, but the raw material cost is high, making large-scale application prohibitively expensive. Common sulfate fillers undergo crystal transformations in hot and humid environments, leading to coating cracking (for example, the phase transition from CaSO₄·2H₂O to CaSO₄ results in a volume shrinkage of 9%). Therefore, we propose a method for preparing a highly efficient radiative cooling coating. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for preparing an efficient radiative cooling coating. Through the lattice doping effect of calcium sulfite and rare earth oxides, the coating achieves synergistic enhancement of full-band sunlight reflection and infrared emission through the atmospheric window. The coating is particularly suitable for surface heat dissipation of buildings and offshore equipment in high-humidity coastal areas, solving the problems raised in the background technology.

[0006] To achieve the above object, the present invention provides the following technical solution: a method for preparing a high-efficiency radiant cooling coating, comprising the following steps:

[0007] Step 1: Add deionized water, mildew and antibacterial agent, wetting and dispersing agent and defoaming agent into a stirring tank and mix at 500-800 rpm for 10 minutes to form a uniform premix;

[0008] Step 2: Add CaSO3 radiation cooling filler, lead-free functional filler, and modified heat reflective TiO2 (rutile type) to the premixed solution in sequence, and disperse at a high speed of 1200-1500 rpm for 30-60 minutes, controlling the temperature to ≤40°C;

[0009] Step 3: Transfer the dispersed slurry to a sand mill and grind it to a fineness of ≤50μm, and cycle 2-3 times to ensure uniformity;

[0010] Step 4: Add SiO2 aerogel nanosheets, single-component fluorosilicone emulsion, water-based acrylic emulsion, film-forming aid, leveling agent, thickener and mildew and antibacterial agent to the ground slurry in batches, and adjust the viscosity to 80-100 KU;

[0011] Step 5: Filter the slurry using a 200-300 mesh filter and perform vacuum degassing with a vacuum degree of -0.08 MPa to -0.09 MPa for 10-20 minutes;

[0012] Step 6: Add pH regulator to adjust the pH of the system to 8.0-9.0, and finally add antifreeze-dissolving agent and stir at low speed for 5 minutes.

[0013] As a preferred embodiment of the present invention, the raw materials of the coating include the following components by weight percentage: 20%-25% deionized water, 5%-8% CaSO3 radiation refrigeration filler, 10%-20% SiO2 aerogel nanosheets, 10%-15% lead-free functional filler, 20%-30% modified heat reflective TiO2 (rutile type), 10%-15% single-component fluorosilicone emulsion, 20%-30% water-based acrylic emulsion, 0.2%-0.5% wetting dispersant, 0.1%-0.2% leveling agent, 0.3%-1% thickener, 0.1%-0.2% anti-mildew and antibacterial agent, 0.5%-1% film-forming aid, 0.2%-0.5% pH regulator, and 0.3%-1% antifreeze-melting aid.

[0014] As a preferred embodiment of the present invention, the raw materials of the coating include the following components by weight percentage: deionized water: 22%, CaSO3 radiation refrigeration filler: 7%, SiO2 aerogel nanosheets: 15%, lead-free functional filler: 12%, modified heat-reflective TiO2 (rutile type): 25%, one-component fluorosilicone emulsion: 12%, water-based acrylic emulsion: 25%, wetting dispersant: 0.4%, leveling agent: 0.15%, thickener: 0.5%, anti-mildew and antibacterial agent: 0.15%, film-forming aid: 0.8%, pH regulator: 0.3%, and antifreeze-melting aid: 0.7%.

[0015] As a preferred embodiment of the present invention, the raw materials of the coating include the following components by weight percentage: deionized water: 24%, CaSO3 radiation refrigeration filler: 6%, SiO2 aerogel nanosheets: 18%, lead-free functional filler: 14%, modified heat-reflective TiO2 (rutile type): 28%, one-component fluorosilicone emulsion: 13%, water-based acrylic emulsion: 22%, wetting dispersant: 0.3%, leveling agent: 0.1%, thickener: 0.8%, anti-mildew and antibacterial agent: 0.1%, film-forming aid: 0.9%, pH regulator: 0.4%, and antifreeze-melting aid: 1.5%.

[0016] As a preferred embodiment of the present invention, the CaSO3 radiation refrigeration filler is a core-shell structure functional filler, the core of which is calcium sulfite, the shell is a rare earth oxide coating layer, and the rare earth oxide is Y2O3.

[0017] As a preferred embodiment of the present invention, the step 2 adopts a staged dispersion method, first premixing at a low speed (800 rpm) for 10 minutes, then dispersing at a high speed (1500 rpm) for 50 minutes, and the temperature is strictly controlled below 35°C.

[0018] As a preferred embodiment of the present invention, the sand mill in step three is cycled three times, and the grinding fineness is ≤40 μm.

[0019] As a preferred embodiment of the present invention, the porosity of the SiO2 aerogel nanosheet is 80%-99.8%, and the specific surface area is ≥1000m 2 / g, density ≤3kg / m 3 The lead-free functional filler is one of ceramic micropowder, glass micropowder or silicon micropowder.

[0020] As a preferred embodiment of the present invention, the lead-free functional filler is one of ceramic micropowder, glass micropowder or silicon micropowder.

[0021] As a preferred embodiment of the present invention, the modified heat-reflective TiO2 (rutile type) is prepared by a sulfuric acid process and has a rod-like structure and large particle size.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The present invention's method for preparing a high-efficiency radiative cooling coating uses calcium sulfite as a core-shell functional filler after an inorganic surface coating treatment. The high reflectivity and low thermal conductivity of calcium sulfite, as well as the stability of the material after coating treatment, achieve dual barriers to both radiative and conductive heat flow, while also possessing the advantages of being lightweight, resistant to extreme environments, and multifunctionally integrated.

[0024] 2. The present invention provides a method for preparing a high-efficiency radiative cooling coating. SiO2 aerogel nanosheets have excellent thermal insulation capabilities. The combination of their internal microporous structure and the low degree of vibration restriction of air molecules enables them to maintain a low thermal conductivity coefficient in high-temperature environments, thereby achieving a highly efficient thermal insulation effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0026] Figure 1 The figure is a flow chart of the method for preparing the high-efficiency radiant cooling coating of the present invention. DETAILED DESCRIPTION

[0027] The present invention provides a method for preparing a high-efficiency radiative cooling coating, which realizes the synergistic enhancement of full-band sunlight reflection and infrared emission from the atmospheric window through the lattice doping effect of calcium sulfite and rare earth oxides. The coating is particularly suitable for surface heat dissipation of buildings and offshore equipment in high-humidity coastal areas. The specific implementation steps are as follows:

[0028] 1. Raw material composition and ratio

[0029] The coating formulation includes the following components by weight percentage:

[0030] Deionized water: 20%-25%, CaSO3 radiation refrigeration filler: 5%-8%, SiO2 aerogel nanosheets: 10%-20%, lead-free functional filler: 10%-15%, modified heat reflective TiO2 (rutile type): 20%-30%, one-component fluorosilicone emulsion: 10%-15%, water-based acrylic emulsion: 20%-30%, wetting and dispersing agent: 0.2%-0.5%, leveling agent: 0.1%-0.2%, thickener: 0.3%-1%, anti-mildew and antibacterial agent: 0.1%-0.2%, film-forming agent: 0.5%-1%, pH regulator: 0.2%-0.5%, antifreeze and melt agent: 0.3%-1%.

[0031] in:

[0032] CaSO3 radiation refrigeration filler is a core-shell functional filler with calcium sulfite that has undergone inorganic surface coating treatment. Through the high reflectivity and low thermal conductivity of calcium sulfite and the stability of the material after coating treatment, it achieves dual barrier of radiation and conduction heat flow, and has the advantages of lightweight, resistance to extreme environments and multifunctional integration.

[0033] SiO2 aerogel nanosheets are a type of nano-lightweight porous material with a complex three-dimensional network structure. Its basic skeleton is composed of amorphous SiO2 and air as its main component. It is a gel material with gas as the dispersion medium. It is a structure-controllable lightweight nanoporous solid material composed of colloidal particles that aggregate with each other and has a continuous three-dimensional network structure. Its solid phase and pore structure are both nanometer-scale, with a porosity of up to 80% to 99.8% and a specific surface area of ​​up to 1000m 2 / g or above, density as low as 3kg / m 3 , is currently the solid material with the smallest density and the best thermal insulation performance.

[0034] Lead-free functional filler is a kind of ceramic / glass micropowder or silica micropowder. It is a non-toxic, odorless, pollution-free inorganic non-metallic material with good temperature resistance, good stability, acid and alkali corrosion resistance, poor thermal conductivity, high insulation, low expansion, stable chemical properties, and high hardness.

[0035] Produced using a sulfuric acid process, modified heat-reflective TiO2 exhibits large particle size, a rod-like structure, and the characteristics of rutile titanium dioxide pigments. This material retains the high hiding power and low photocatalytic activity of titanium oxide pigments while significantly improving heat reflectivity, making it an ideal choice for applications requiring heat shielding properties, such as coatings and plastics.

[0036] Fluorosilicone emulsion is an emulsion modified by introducing organic fluorine and organic silicone functional monomers. It has excellent weather resistance, durability, chemical resistance, corrosion resistance, insulation, non-flammability and low-temperature flexibility. This emulsion is usually made by multi-polymerization and has acid and alkali resistance, salt spray resistance, whitening resistance, high weather resistance, hydrophobicity and oleophobicity.

[0037] The water-based acrylic emulsion is at least one of an economical styrene acrylic exterior wall flat coating emulsion, a high-performance pure acrylic emulsion, and a silicone acrylic high-performance exterior wall flat coating emulsion.

[0038] The wetting and dispersing agent is a non-ionic water-based high-efficiency dispersant from HYMINUS. It is a VOC-free and low-gassing non-ionic wetting and dispersing agent for water-based coatings. Its unique composition has a strong affinity for the surfaces of various hydrophilic materials and fillers, demonstrating excellent wetting and dispersing effects.

[0039] The leveling agent is Digao 450 leveling agent, which is a smoothing and flow aid that can be widely used in water-based leveling agents. It has anti-cratering, fluidity, anti-adhesion / peeling effects, good compatibility (reduced risk of fogging), and can also prevent the occurrence of defects such as craters and orange peel in the coating film.

[0040] The thickener is hydroxyethyl cellulose.

[0041] The anti-mildew and antibacterial agent is a TROY composite anti-mildew and antibacterial agent, which combines the long-lasting effect of inorganic antibacterial agents and the strong antibacterial properties of organic antibacterial agents. It has a good inhibitory effect on various microorganisms and is highly safe.

[0042] The film-forming aid is alcohol ester dodecanone film-forming aid.

[0043] The pH regulator is G-95MPH regulator.

[0044] The antifreeze-thaw aid is propylene glycol antifreeze-thaw aid.

[0045] [SO3] of CaSO3 2 -The group produces multiple infrared absorption peaks in the range of 7-14μm (verified by FTIR), and the absorption peak position and intensity can be controlled by rare earth doping.

[0046] A "core-shell structure stress buffer model" was established, proving that the Y2O3 coating can inhibit the oxidation of CaSO3 to CaSO4 (XPS detection shows that the valence state of the surface sulfur element remains +4), and the crystal phase is stable after 1000h of wet-heat aging (XRD half-peak width change is <0.01°).

[0047] 2. The specific production steps are as follows:

[0048] 1. Premixing: Add deionized water, antifungal agent, wetting dispersant and defoaming agent into a stirring tank and mix at 500-800 rpm for 10 minutes to form a uniform premix.

[0049] 2. Dispersion of pigments and fillers: Add CaSO3 radiation refrigeration filler, lead-free functional filler and modified heat reflective TiO2 to the premixed liquid in sequence, disperse at a high speed of 1200-1500 rpm for 30-60 minutes, and control the temperature to ≤40°C.

[0050] 3. Grinding: Transfer the dispersed slurry to a sand mill and grind it to a fineness of ≤50 μm (detected by a Hegman fineness meter), and cycle 2-3 times to ensure uniformity.

[0051] 4. Paint adjustment: Add SiO2 aerogel nanosheets, one-component fluorosilicone emulsion, water-based acrylic emulsion, film-forming aid, leveling agent, thickener and mildew and antibacterial agent to the ground slurry in batches, and adjust the viscosity to 80-100 KU (Brookfield viscometer test).

[0052] 5. Filtration and degassing: Filter the slurry through a 200-300 mesh filter and, if necessary, perform vacuum degassing (vacuum degree -0.08 MPa, degassing time 10-20 minutes). Add a pH adjuster to adjust the system pH to 8.0-9.0, and finally add an antifreeze aid and stir at a low speed (200-300 rpm) for 5 minutes.

[0053] The innovative application basis of calcium sulfite in this application has the following characteristics:

[0054] Spectral characteristics: Calcium sulfite (band gap 4.1eV) has a reflectivity of >96% in the 0.3-2.5μm band (UV-Vis-NIR test), and its SO3 2 - The group produces strong infrared absorption at 8-13 μm (FTIR verification);

[0055] Stability advantage: Comparative experiments show that the volume expansion rate of CaSO3 in an 85% RH environment is only 0.7%, which is much lower than CaCO3 (3.2%) and CaSO4 (2.1%).

[0056] Example 1

[0057] The coating formulation includes the following components by weight percentage:

[0058] Deionized water: 22%, CaSO3 radiation refrigeration filler: 7%, SiO2 aerogel nanosheets: 15%, lead-free functional filler: 12%, modified heat reflective TiO2 (rutile type): 25%, one-component fluorosilicone emulsion: 12%, water-based acrylic emulsion: 25%, wetting and dispersing agent: 0.4%, leveling agent: 0.15%, thickener: 0.5%, anti-mildew and antibacterial agent: 0.15%, film-forming agent: 0.8%, pH regulator: 0.3%, antifreeze and melt agent: 0.7%.

[0059] During the preparation process, the following adjustments were also made:

[0060] Pigment and filler dispersion: Use a staged dispersion method, premix at low speed (800 rpm) for 10 minutes, then disperse at high speed (1500 rpm) for 50 minutes. The temperature is strictly controlled below 35°C.

[0061] Grinding: Increase the number of sand mill cycles to 3 times to ensure fineness ≤ 40μm.

[0062] Example 2

[0063] The coating formulation includes the following components by weight percentage:

[0064] Deionized water: 24%, CaSO3 radiation refrigeration filler: 6%, SiO2 aerogel nanosheets: 18%, lead-free functional filler: 14%, modified heat reflective TiO2 (rutile type): 28%, one-component fluorosilicone emulsion: 13%, water-based acrylic emulsion: 22%, wetting and dispersing agent: 0.3%, leveling agent: 0.1%, thickener: 0.8%, anti-mildew and antibacterial agent: 0.1%, film-forming agent: 0.9%, pH regulator: 0.4%, antifreeze and melt agent: 1.5%.

[0065] During the preparation process, the following adjustments were also made:

[0066] Post-processing enhancement: degassing time is extended to 20 minutes and vacuum degree is increased to -0.09MPa.

[0067] Comparison of experimental data:

[0068]

[0069] Referring to the comparative data of the examples, it can be seen that the optical performance (reflectivity +1.2%) and thermal insulation effect are significantly improved by optimizing the dispersion process and grinding fineness, and the method is suitable for high-efficiency refrigeration scenarios.

[0070] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, from all points of view, the embodiments should be regarded as illustrative and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes that fall within the meaning and range of equivalents of the claims are included in the present invention. Any reference signs in the claims should not be construed as limiting the claim to which they relate.

[0071] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A method for preparing a high-efficiency radiant cooling coating, characterized in that: The following steps are involved: Step 1: Add deionized water, mildew and antibacterial agent, wetting and dispersing agent and defoaming agent into a stirring tank and mix at 500-800 rpm for 10 minutes to form a uniform premix; Step 2: Add CaSO3 radiation cooling filler, lead-free functional filler, and modified heat reflective TiO2 (rutile type) to the premixed solution in sequence, and disperse at a high speed of 1200-1500 rpm for 30-60 minutes, controlling the temperature to ≤40°C; Step 3: Transfer the dispersed slurry to a sand mill and grind it to a fineness of ≤50μm, and cycle 2-3 times to ensure uniformity; Step 4: Add SiO2 aerogel nanosheets, single-component fluorosilicone emulsion, water-based acrylic emulsion, film-forming aid, leveling agent, thickener and mildew and antibacterial agent to the ground slurry in batches, and adjust the viscosity to 80-100 KU; Step 5: Filter the slurry using a 200-300 mesh filter and perform vacuum degassing with a vacuum degree of -0.08 MPa to -0.09 MPa for 10-20 minutes; Step 6: Add pH regulator to adjust the pH of the system to 8.0-9.0, and finally add antifreeze-dissolving agent and stir at low speed for 5 minutes.

2. The method for preparing a high-efficiency radiant cooling coating according to claim 1, characterized in that: The raw materials of the coating include the following components by weight percentage: 20%-25% of deionized water, 5%-8% of CaSO3 radiation refrigeration filler, 10%-20% of SiO2 aerogel nanosheets, 10%-15% of lead-free functional filler, 20%-30% of modified heat-reflective TiO2 (rutile type), 10%-15% of single-component fluorosilicone emulsion, 20%-30% of water-based acrylic emulsion, 0.2%-0.5% of wetting dispersant, 0.1%-0.2% of leveling agent, 0.3%-1% of thickener, 0.1%-0.2% of mildew and antibacterial agent, 0.5%-1% of film-forming aid, 0.2%-0.5% of pH regulator, and 0.3%-1% of antifreeze-melting aid.

3. The method for preparing a high-efficiency radiant cooling coating according to claim 2, characterized in that: The raw materials of the coating include the following components by weight percentage: deionized water: 22%, CaSO3 radiation refrigeration filler: 7%, SiO2 aerogel nanosheets: 15%, lead-free functional filler: 12%, modified heat-reflective TiO2 (rutile type): 25%, one-component fluorosilicone emulsion: 12%, water-based acrylic emulsion: 25%, wetting dispersant: 0.4%, leveling agent: 0.15%, thickener: 0.5%, anti-mildew and antibacterial agent: 0.15%, film-forming aid: 0.8%, pH regulator: 0.3%, and antifreeze-thaw aid: 0.7%.

4. The method for preparing a high-efficiency radiant cooling coating according to claim 2, wherein: The raw materials of the coating include the following components by weight percentage: deionized water: 24%, CaSO3 radiation refrigeration filler: 6%, SiO2 aerogel nanosheets: 18%, lead-free functional filler: 14%, modified heat-reflective TiO2 (rutile type): 28%, single-component fluorosilicone emulsion: 13%, water-based acrylic emulsion: 22%, wetting dispersant: 0.3%, leveling agent: 0.1%, thickener: 0.8%, anti-mildew and antibacterial agent: 0.1%, film-forming aid: 0.9%, pH regulator: 0.4%, and antifreeze-melting aid: 1.5%.

5. The method for preparing a high-efficiency radiant cooling coating according to claim 2, characterized in that: The CaSO3 radiation refrigeration filler is a core-shell structure functional filler, the core of which is calcium sulfite, the shell is a rare earth oxide coating layer, and the rare earth oxide is Y2O3.

6. The method for preparing a high-efficiency radiant cooling coating according to claim 1, characterized in that: In the second step, a staged dispersion method is adopted, first premixing at a low speed (800 rpm) for 10 minutes, then dispersing at a high speed (1500 rpm) for 50 minutes, and the temperature is strictly controlled below 35°C.

7. The method for preparing a high-efficiency radiant cooling coating according to claim 1, characterized in that: In the step 3, the sand mill is cycled 3 times, and the grinding fineness is ≤40 μm.

8. The method for preparing a high-efficiency radiant cooling coating according to claim 2, characterized in that: The porosity of the SiO2 aerogel nanosheet is 80%-99.8%, and the specific surface area is ≥1000m 2 / g, density ≤3kg / m 3 .

9. The method for preparing a high-efficiency radiant cooling coating according to claim 2, characterized in that: The lead-free functional filler is one of ceramic micropowder, glass micropowder or silicon micropowder.

10. The method for preparing a high-efficiency radiant cooling coating according to claim 2, characterized in that: The modified heat-reflective TiO2 (rutile type) is prepared by a sulfuric acid process and has a rod-like structure and large particle size characteristics.

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