An aerogel thermal radiation barrier coating and its preparation method

Abstract

This invention discloses an aerogel thermal radiation barrier coating, comprising a hybrid porous microsphere material. The coating of this invention has excellent high-efficiency thermal insulation and crack resistance. The aerogel mesopores and hollow glass microsphere cavities in the hybrid porous microspheres form a multi-level thermal resistance barrier, which greatly extends the heat conduction path. Rutile nano-titanium dioxide and potassium hexatitanate whiskers have high reflectivity to near-infrared light, making the coating's equivalent thermal conductivity ≤0.028W / m·K.

Description

Technical Field

[0001] This invention relates to the field of architectural coatings technology, specifically to an aerogel thermal radiation barrier intermediate coating for building exterior walls, and more particularly to an aerogel thermal radiation barrier intermediate coating containing hybrid porous microsphere materials and its preparation method. Background Technology

[0002] Exterior wall insulation is a key aspect of reducing building energy consumption and improving living comfort. Existing exterior wall insulation coatings are mainly classified into three types: barrier, reflective, and radiative. Among them, aerogel, due to its extremely low thermal conductivity, has become an ideal barrier and insulation filler.

[0003] However, existing aerogel thermal insulation coatings have the following technical defects: 1. Poor compatibility between aerogel and the substrate: The large difference in polarity at the interface between hydrophobic aerogel and hydrophilic polymer emulsion makes them prone to aggregation and sedimentation, resulting in uneven thermal insulation performance of the coating. 2. When the proportion of aerogel added is high, the coating becomes brittle, its flexibility decreases, and its adhesion weakens, limiting the improvement of thermal insulation performance. 3. Most products rely solely on barrier insulation, with poor synergistic mechanisms. 4. The coating is prone to microcracks: Stress generated by curing shrinkage and temperature changes leads to the propagation of microcracks, shortening the coating life.

[0004] To address the aforementioned issues, those skilled in the art have attempted to combine aerogels with hollow glass microspheres, nano-titanium dioxide, and other materials. However, these methods are mostly simple physical mixtures, lacking chemical bonding between fillers, resulting in weak interfacial bonding and failing to resolve stress cracking problems.

[0005] Therefore, it is urgent to develop a mid-coat paint that combines multiple heat insulation mechanisms, high mechanical strength, crack resistance, and easy application. Summary of the Invention

[0006] The purpose of this invention is to provide an aerogel thermal radiation barrier coating.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: An aerogel heat radiation barrier coating, characterized in that it comprises the following raw materials in parts by weight: 25–40 parts of silicone-modified acrylate emulsion; 15–30 parts of hybrid porous microsphere material; 8–15 parts of rutile nano-titanium dioxide; 3–8 parts of potassium hexatite whiskers; 2–4 parts of film-forming aid; 1–2 parts dispersant; Wetting agent 0.5–1 part; Defoamer 0.3–0.8 parts; Thickener 0.2–0.6 parts; Preservative: 0.2–0.5 parts; 20–35 parts deionized water; The hybrid porous microsphere material is a porous composite microsphere formed by polysiloxane as the main chain, embedded with hollow glass microspheres and silica aerogel.

[0008] The preparation method of the hybrid porous microsphere material includes the following steps: (1) Add 100 parts by weight of hydroxyl-terminated polydimethylsiloxane, 15-25 parts by weight of methyltriethoxysilane, and 5-10 parts by weight of dimethyldiethoxysilane to a reaction vessel, add 80-120 parts by weight of anhydrous ethanol and 10-20 parts by weight of deionized water, adjust the pH to 4-5, stir at room temperature for 30-40 minutes; raise the temperature to 60-70℃, add 0.1-0.3 parts by weight of dibutyltin dilaurate, react for 2-3 hours, and obtain polysiloxane prepolymer sol; (2) Add 30-50 parts by weight of hollow glass microspheres and 20-40 parts by weight of silica aerogel powder to the prepolymer sol while stirring at 300-500 rpm, and continue stirring for 15-20 minutes to obtain a mixed slurry; (3) The mixed slurry is spray-dried to form spherical particles; (4) Vacuum solidify the spherical particles at 100-120℃ for 4-6 hours, cool and sieve to obtain hybrid porous microsphere material.

[0009] The solid content of the organosilicon-modified acrylate emulsion is 45-50%, and the organosilicon monomer content accounts for 5-15% of the total polymer.

[0010] The film-forming aid is one or more of dodecyl alcohol ester, dodecyl alcohol ester, or dipropylene glycol butyl ether; the dispersant is a sodium polycarboxylate or ammonium salt dispersant; the wetting agent is a polyether-modified polysiloxane wetting agent; the defoamer is a mineral oil or organosilicon defoamer; the thickener is a hydrophobically modified alkali-swellable or polyurethane-associated thickener; and the preservative is an isothiazolinone preservative.

[0011] A method for preparing an aerogel thermal radiation barrier coating includes the following steps: (1) Under stirring at 300-500 rpm, slowly add the hybrid porous microsphere material to deionized water, add dispersant and wetting agent, increase the speed to 800-1200 rpm and disperse for 10-15 minutes to obtain microsphere pre-dispersion slurry; (2) Rutile nano-titanium dioxide and potassium hexatitanate whiskers are premixed at 500-800 rpm to obtain a mixed filler; (3) While stirring at 500-800 rpm, add microsphere pre-dispersed slurry and mixed filler to silicone-modified acrylate emulsion in sequence, and increase the speed to 1000-1500 rpm to disperse for 15-25 minutes; (4) While stirring at 800-1000 rpm, add film-forming aid, defoamer, thickener and preservative in sequence, and stir for 10-15 minutes; (5) Adjust the viscosity with deionized water to 60-80 seconds at 25°C in a Fort Worcestershire cup, let stand for 15-30 minutes to defoam, then filter and package.

[0012] The coating in this invention has excellent heat insulation and crack resistance. The aerogel mesopores and hollow glass microsphere cavities in the hybrid porous microspheres form a multi-level thermal resistance barrier, which greatly extends the heat conduction path. The rutile nano titanium dioxide and potassium hexatitanate whiskers have high reflectivity to near-infrared light, making the coating's equivalent thermal conductivity ≤0.028W / m·K.

[0013] The potassium hexatitanate whiskers of the present invention are commonly used fillers in the field, and their combination with aerogels and hollow glass microspheres is also commonly used in the prior art. However, the whisker-like morphology of potassium hexatitanate whiskers can work synergistically with the flexible segments of polysiloxane during coating curing shrinkage and thermal expansion and contraction to absorb and disperse stress and prevent microcrack propagation. Compared with the mixed addition system of direct fillers, it can significantly improve the crack resistance and toughness of the coating. At the same time, the Si-OH or Ti-OH on the surface of the whiskers can undergo dehydration condensation with the active groups of the polysiloxane prepolymer to form continuous Si-O-Ti chemical bonds. The prepolymer sol of this invention inherently contains a high density of unreacted alkoxy and silanol groups. After the filler is added, the Si-OH groups on the surface directly undergo dehydration condensation with the active groups in the prepolymer sol, forming continuous Si-O-Si chemical bonds. Through low-speed stirring and thorough wetting, the prepolymer sol achieves complete wetting of the filler while avoiding damage to the aerogel structure, creating a maximized interfacial contact area for subsequent chemical bonding. Compared to the existing method of composite filler with resin matrix treated with silane coupling agents, the bonding of this invention is more direct and thorough, avoiding interfacial bonding defects caused by uneven coupling agent treatment, insufficient hydrolysis of the coupling agent, or poor orientation of coupling agent molecules on the filler surface. Traditional coatings containing polysiloxane materials primarily use polysiloxanes as film-forming bases or resin matrices, with aerogel powder, hollow glass microspheres, potassium hexatitanate whiskers, etc., dispersed as fillers. The fillers and matrix are physically blended together. Surface modification of aerogel powder (such as silane coupling agent treatment) may improve compatibility to some extent, but the bonding between fillers and resin remains mainly interfacial physical, failing to achieve chemical bonding and structural integration between fillers. Furthermore, traditional polysiloxane resins only serve as film-forming bases and do not undertake active stress dispersion functions. In contrast, the method of this invention transforms the fillers from simple dispersed phases into a covalently bonded whole with the matrix. The product of this invention has good construction adaptability, excellent compatibility between microspheres and emulsion, does not settle, has storage stability of ≥12 months, and can achieve a single-layer construction thickness of 1.5-2.0 mm. Attached Figure Description

[0014] Figure 1 This is the first page of the sampling inspection report for the product of this invention; Figure 2 This is the test result page of the sampling inspection report for the product of this invention. Detailed Implementation Example 1

[0015] I. Preparation of Hybrid Porous Microsphere Materials Weigh the raw materials according to the following parts by weight: 100 parts of hydroxyl-terminated polydimethylsiloxane (molecular weight 3000, hydroxyl content 3%); 20 parts of methyltriethoxysilane; 8 parts of dimethyldiethoxysilane; 100 parts of anhydrous ethanol; 15 parts of deionized water; 0.2 parts of dibutyltin dilaurate; 40 parts of hollow glass microspheres (true density 0.3 g / cm³, particle size 30-60 μm); and 30 parts of silica aerogel powder (particle size 20-40 μm, porosity 92%, thermal conductivity 0.018 W / m·K).

[0016] Preparation steps: (1) Add hydroxyl-terminated polydimethylsiloxane, methyltriethoxysilane and dimethyldiethoxysilane to a reaction vessel, add anhydrous ethanol and deionized water, adjust the pH to 4.5 with glacial acetic acid, stir at room temperature for 30 minutes; heat to 65°C, add dibutyltin dilaurate, react for 2.5 hours to obtain prepolymer sol; (2) While stirring at 400 rpm, the hollow glass microspheres and silica aerogel powder were slowly added to the prepolymer sol, and stirring was continued for 18 minutes to obtain a mixed slurry; (3) Spray dry the mixed slurry: inlet temperature 160℃, outlet temperature 90℃, atomizer speed 18000 rpm, collect microspheres; (4) Place the microspheres in a vacuum drying oven and cure at 110°C for 5 hours. After cooling, sieve to obtain hybrid porous microsphere material (particle size 10-80 μm).

[0017] II. Preparation of Aerogel Thermal Radiation Barrier Coating Weigh the raw materials according to the following weight proportions: 32 parts of silicone-modified acrylate emulsion (48% solids, 10% silicone); 22 parts of the above-mentioned hybrid porous microsphere material; 12 parts of rutile nano-titanium dioxide (average particle size 200 nm); 5 parts of potassium hexatite whiskers (aspect ratio 15, average length 20 μm); 3 parts of dodecyl alcohol ester; 1.5 parts of sodium polycarboxylate dispersant; 0.8 parts of polyether-modified polysiloxane wetting agent; 0.5 parts of silicone defoamer; 0.4 parts of hydrophobic modified alkali-swellable thickener; 0.3 parts of isothiazolinone preservative; and 28 parts of deionized water.

[0018] Preparation steps: (1) Under stirring at 400 rpm, the hybrid porous microsphere material was slowly added to deionized water, along with a dispersant and a wetting agent. The stirring speed was increased to 1000 rpm and the mixture was dispersed for 12 minutes to obtain a microsphere pre-dispersion slurry. (2) Nano-titanium dioxide and potassium hexatitanate whiskers were premixed at 600 rpm for 5 minutes to obtain a mixed filler; (3) While stirring at 600 rpm, add microsphere pre-dispersed slurry and mixed filler to the silicone-modified acrylate emulsion in sequence, and increase the speed to 1200 rpm to disperse for 20 minutes; (4) While stirring at 900 rpm, add film-forming aid, defoamer, thickener and preservative in sequence, and stir for 12 minutes; (5) Adjust the viscosity with deionized water to 70 seconds (25°C) of the fourth cup, let it stand for 20 minutes to defoam, filter and package to obtain the finished product. Example 2

[0019] The preparation method of the hybrid porous microsphere material includes the following steps: 100 parts by weight of hydroxyl-terminated polydimethylsiloxane, 15 parts by weight of methyltriethoxysilane, and 5 parts by weight of dimethyldiethoxysilane were added to a reaction vessel, along with 80 parts by weight of anhydrous ethanol and 10 parts by weight of deionized water. The pH was adjusted to 4, and the mixture was stirred at room temperature for 30 minutes. The temperature was then raised to 60°C, and 0.1 parts by weight of dibutyltin dilaurate were added. The reaction was carried out for 2 hours to obtain a polysiloxane prepolymer sol. (2) 30 parts by weight of hollow glass microspheres and 20 parts by weight of silica aerogel powder were slowly added to the prepolymer sol under stirring at 300 rpm, and stirring was continued for 15 minutes to obtain a mixed slurry; (3) The mixed slurry is spray-dried to form spherical particles; (4) The spherical particles were vacuum solidified at 120°C for 4 hours, cooled and sieved to obtain hybrid porous microsphere material.

[0020] The preparation of the aerogel thermal radiation barrier coating is the same as in Example 1, except that the proportions are adjusted as follows: 35 parts of silicone-modified acrylate emulsion, 18 parts of hybrid porous microsphere material, 15 parts of nano titanium dioxide, 6 parts of potassium hexatitanate whiskers, 3.5 parts of film-forming aid, 1.2 parts of dispersant, 0.6 parts of wetting agent, 0.4 parts of defoamer, 0.5 parts of thickener, 0.3 parts of preservative, and 25 parts of deionized water. Example 3

[0021] The preparation method of hybrid porous microsphere materials includes the following steps: (1) 100 parts by weight of hydroxyl-terminated polydimethylsiloxane, 25 parts by weight of methyltriethoxysilane and 10 parts by weight of dimethyldiethoxysilane were added to a reaction vessel, 120 parts by weight of anhydrous ethanol and 20 parts by weight of deionized water were added, the pH was adjusted to 5, and the mixture was stirred at room temperature for 40 minutes; the temperature was raised to 70°C, 0.3 parts by weight of dibutyltin dilaurate were added, and the reaction was carried out for 3 hours to obtain polysiloxane prepolymer sol; (2) 50 parts by weight of hollow glass microspheres and 40 parts by weight of silica aerogel powder were slowly added to the prepolymer sol under stirring at 500 rpm, and stirring was continued for 20 minutes to obtain a mixed slurry; (3) The mixed slurry is spray-dried to form spherical particles; (4) The spherical particles were vacuum-cured at 100°C for 6 hours, cooled and sieved to obtain hybrid porous microspheres. The preparation of the gel thermal radiation barrier coating is the same as in Example 1, except that the proportions are adjusted as follows: 28 parts of silicone-modified acrylate emulsion, 25 parts of hybrid porous microsphere material, 10 parts of nano titanium dioxide, 4 parts of potassium hexatitanate whiskers, 2.5 parts of film-forming aid, 1.8 parts of dispersant, 0.9 parts of wetting agent, 0.6 parts of defoamer, 0.3 parts of thickener, 0.4 parts of preservative, and 32 parts of deionized water.

[0022] Comparative Example 1 (physical mixing of ordinary aerogel and hollow microspheres, without hybrid microspheres) 32 parts of organosilicon-modified acrylate emulsion; 12 parts of hydrophobic silica aerogel powder (not pre-formed into microspheres); 10 parts of hollow glass microspheres; 12 parts of nano titanium dioxide; 5 parts of potassium hexatitanate whiskers; and other additives and dosages as in Example 1.

[0023] Preparation method: Aerogel, hollow microspheres, nano titanium dioxide, potassium hexatitanate whiskers are directly mixed and dispersed with emulsion.

[0024] Comparative Example 2 (without potassium hexatite whiskers) Same as Example 1, but potassium hexatitanate whiskers were removed, and nano titanium dioxide was increased to 17 parts.

[0025] Performance testing The intermediate coatings of Examples 1-3 and Comparative Examples 1-2 were applied to a 100mm×100mm×5mm float glass plate, and the dry film thickness was controlled at 1.5mm. The coatings were tested after curing for 7 days.

[0026] Equivalent thermal conductivity (W / m·K) 0.026 0.024 0.027 0.032 0.028 GB / T 10294 Solar reflectance 0.86 0.87 0.85 0.84 0.83 GJB 2502 Coating adhesion (grade) 1 1 0 2 1 GB / T 9286 Flexibility (mm) 2 2 2 4 3 GB / T 1731 Impact resistance (cm·kg) 55 50 60 39 46 GB / T 1732 Thermal cycling (-20℃ / 80℃, 200 cycles) No cracks No cracks No cracks Localized microcracks Microcracks at the edge / Storage stability (12 months, settling rate %) 4.2 4.5 3.8 12.5 6.2 / The product of this invention was also commissioned to a third party for testing, and some of the test results are shown in the accompanying drawings of the specification.

Claims

1. An aerogel thermal radiation barrier coating, characterized in that, The following ingredients are included in parts by weight: 25–40 parts of silicone-modified acrylate emulsion; 15–30 parts of hybrid porous microsphere material; 8–15 parts of rutile nano-titanium dioxide; 3–8 parts of potassium hexatite whiskers; 2–4 parts of film-forming aid; 1–2 parts dispersant; Wetting agent 0.5–1 part; Defoamer 0.3–0.8 parts; Thickener 0.2–0.6 parts; Preservative: 0.2–0.5 parts; 20–35 parts deionized water; The hybrid porous microsphere material is a porous composite microsphere formed by polysiloxane as the main chain, embedded with hollow glass microspheres and silica aerogel.

2. The aerogel thermal radiation barrier coating according to claim 1, characterized in that, The preparation method of the hybrid porous microsphere material includes the following steps: (1) Add 100 parts by weight of hydroxyl-terminated polydimethylsiloxane, 15-25 parts by weight of methyltriethoxysilane, and 5-10 parts by weight of dimethyldiethoxysilane to a reaction vessel, add 80-120 parts by weight of anhydrous ethanol and 10-20 parts by weight of deionized water, adjust the pH to 4-5, stir at room temperature for 30-40 minutes; raise the temperature to 60-70℃, add 0.1-0.3 parts by weight of dibutyltin dilaurate, react for 2-3 hours, and obtain polysiloxane prepolymer sol; (2) Add 30-50 parts by weight of hollow glass microspheres and 20-40 parts by weight of silica aerogel powder to the prepolymer sol while stirring at 300-500 rpm, and continue stirring for 15-20 minutes to obtain a mixed slurry; (3) The mixed slurry is spray-dried to form spherical particles; (4) Vacuum solidify the spherical particles at 100-120℃ for 4-6 hours, cool and sieve to obtain hybrid porous microsphere material.

3. The aerogel thermal radiation barrier coating according to claim 1, characterized in that, The solid content of the organosilicon-modified acrylate emulsion is 45-50%, and the organosilicon monomer content accounts for 5-15% of the total polymer.

4. The aerogel thermal radiation barrier coating according to claim 1, characterized in that, The film-forming aid is one or more of dodecyl alcohol ester, dodecyl alcohol ester, or dipropylene glycol butyl ether; the dispersant is a sodium polycarboxylate or ammonium salt dispersant; the wetting agent is a polyether-modified polysiloxane wetting agent; the defoamer is a mineral oil or organosilicon defoamer; the thickener is a hydrophobically modified alkali-swellable or polyurethane-associated thickener; and the preservative is an isothiazolinone preservative.

5. A method for preparing an aerogel thermal radiation barrier coating as described in any one of claims 1-4, characterized in that, Includes the following steps: (1) Under stirring at 300-500 rpm, slowly add the hybrid porous microsphere material to deionized water, add dispersant and wetting agent, increase the speed to 800-1200 rpm and disperse for 10-15 minutes to obtain microsphere pre-dispersion slurry; (2) Rutile nano-titanium dioxide and potassium hexatitanate whiskers are premixed at 500-800 rpm to obtain a mixed filler; (3) While stirring at 500-800 rpm, add microsphere pre-dispersed slurry and mixed filler to silicone-modified acrylate emulsion in sequence, and increase the speed to 1000-1500 rpm to disperse for 15-25 minutes; (4) While stirring at 800-1000 rpm, add film-forming aid, defoamer, thickener and preservative in sequence, and stir for 10-15 minutes; (5) Adjust the viscosity with deionized water to 60-80 seconds at 25°C in a Fort Worcestershire cup, let stand for 15-30 minutes to defoam, then filter and package.

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