Water-based thermal insulation coating prepared based on hydrophobic silicon dioxide aerogel and preparation method of water-based thermal insulation coating

Abstract

The invention provides a high-adhesion water-based aerogel heat insulation coating and a preparation method thereof. According to the method, through a unique process route and formula design, the content of a cosolvent in a two-component waterborne epoxy system is reduced, the problem that an aerogel coating collapses when encountering a solvent is effectively solved, aerogel can be used for the high-strength waterborne epoxy system, it is guaranteed that the coating has good heat insulation performance, meanwhile, the coating strength is improved, and the service life of the coating is prolonged. And the adhesive force of the coating is stabilized to be greater than 1.5 MPa.

Description

Technical Field

[0001] This invention relates to a high-adhesion waterborne aerogel thermal insulation coating and its preparation method, belonging to the field of thermal insulation coatings. Background Technology

[0002] With the increasing demand for building energy conservation and industrial insulation, thermal insulation coatings have received widespread attention due to their convenient construction and flexible application. Silica aerogel, as a nanoporous material, has an extremely low thermal conductivity, making it an ideal and efficient thermal insulation material. Applying it to coatings can significantly improve the thermal insulation performance of the coating.

[0003] The core value of silica aerogel lies in its extremely low thermal conductivity, a property entirely dependent on its three-dimensional porous network structure (porosity typically >90%, nanometer-scale size, and pores filled with static air). The surface of silica aerogel contains numerous silanol groups (-Si-OH), an inherent chemical structure. These silanol groups are highly polar and bind to water molecules through hydrogen bonds, resulting in a strong adsorption capacity for water or moisture. After absorbing water, the thermal conductivity of the aerogel increases dramatically, losing its insulating properties. Therefore, silica aerogel must undergo hydrophobic modification before it can be used as an insulation material.

[0004] The existing aerogel thermal insulation coatings generally have poor adhesion, mainly due to the following two reasons: (1) Poor adhesion is caused by the structure of aerogel itself and the high amount added to the coating. The high porosity of aerogel makes its nanoskeleton thin and has few connection points. It exists in the coating as powder particles, with only point contact between particles, resulting in weak mechanical support. Furthermore, a large amount of aerogel is required to significantly reduce the thermal conductivity of the coating material. The result of introducing a large amount is that it seriously damages the density and continuity of the coating, leading to a significant decrease in coating strength. It cannot withstand external impact, and the adhesion test shows that the coating is cohesively destroyed. The adhesion of existing aerogel thermal insulation coatings can only reach 0.5 MPa or lower. (2) The low strength of the resin system suitable for aerogel coatings leads to poor adhesion. Generally, the strength of the coating resin system is higher for solvent-based systems than for water-based systems, and higher for two-component systems than for one-component systems. Aerogels used in thermal insulation coatings are all hydrophobically modified. The surface of hydrophobically modified aerogels is oleophilic. When used in solvent-based coating systems, the solvent can quickly wet the aerogel surface, generating strong capillary forces that cause the aerogel structure to collapse. This collapse is further exacerbated during the drying process, leading to a loss of the aerogel's thermal insulation properties. Therefore, aerogels can only be used in water-based coating systems and are sensitive to the co-solvent content in these systems. High co-solvent content in water-based coatings can also cause aerogel structure collapse during application. Currently, the only mature applications of aerogels are in water-based systems with almost no co-solvents, such as single-component water-based acrylic emulsions. Acrylic emulsion systems themselves have low strength, resulting in low coating strength for aerogel coating systems. The purpose of this invention is to overcome the shortcomings of existing technologies by improving the aerogel coating resin system and providing a method for preparing a high-adhesion water-based aerogel thermal insulation coating. This method, through a unique process route and formulation design, reduces the content of co-solvents in the two-component waterborne epoxy system, effectively solving the problem of aerogel coatings collapsing when exposed to solvents. This allows aerogels to be used in high-strength waterborne epoxy systems, improving coating strength while ensuring good thermal insulation properties, and making the coating adhesion stable at greater than 1.5 MPa. Summary of the Invention

[0005] This invention improves the adhesion of aerogel thermal insulation coatings through two technical approaches. First, by treating the waterborne resin system, hydrophobic aerogels can be used in two-component waterborne epoxy systems. Second, through coating formulation design, long fiber structures are introduced into the coating formulation to reinforce the system, thereby enhancing the adhesion of the coating system. Waterborne aerogel thermal insulation coatings prepared using this method exhibit adhesion exceeding 1.5 MPa.

[0006] The technical solution of the present invention is as follows: a high-adhesion waterborne heat insulation coating based on hydrophobic silica aerogel, consisting of component A and component B, which are mixed evenly before use.

[0007] Component A is formulated as follows by mass percentage: Deionized water 25.0%~38.0% Preservative and bactericide: 0.15%–0.20% Wetting agent 0.05%~0.1% Dispersant 1.0%–1.2% Defoamer 0.2%–0.4% Aerogel 4.0%–6.0% Titanium dioxide 1.0%~3.0% Ceramic fiber 10.0%~14.0% Waterborne epoxy emulsion 28.0%–32.0% Microbeads 15%–17% Defoamer 0.4%–0.6% Thickener 1.2%–1.5% The formulation of component B, by mass percentage, is as follows: 100% water-based epoxy curing agent An important feature of a high-adhesion waterborne thermal insulation coating based on hydrophobic silica aerogel is that it is based on a two-component waterborne epoxy system, consisting of components A and B, with the following ratio calculated as follows: Amount of epoxy group in component A : Amount of active hydrogen in component B curing agent = 100 : 80-100.

[0008] The co-solvent content of component A, the waterborne epoxy emulsion, must be below 10 g / L. It can be a commercially available waterborne epoxy emulsion or it can be produced through reprocessing. If the VOC content of a commercially available waterborne epoxy emulsion is higher than 10 g / L, it can be reduced to below 10 g / L using vacuum stripping, steam stripping, or membrane separation techniques. The co-solvent content of component B, the waterborne epoxy curing agent, must also be below 10 g / L. It can be a commercially available waterborne epoxy curing agent or it can be produced through reprocessing. If the VOC content of a commercially available waterborne epoxy curing agent is higher than 10 g / L, it can be reduced to below 10 g / L using vacuum stripping, steam stripping, or membrane separation techniques.

[0009] The preparation process of the coating is as follows: Preparation of Component A: Under low-speed stirring, deionized water, preservative, wetting agent, dispersant, and defoamer were added sequentially to the mixing tank and stirred for 5 minutes. Then, aerogel was slowly sprinkled in, and the speed was increased to disperse for 60 minutes. After that, the speed was reduced, titanium dioxide and ceramic fiber were added and stirred for 25 minutes. Then, water-based epoxy emulsion was slowly added and stirred evenly. Microbeads and defoamer were added and stirred for 30 minutes. Finally, thickener was added and stirred for 20 minutes to obtain Component A.

[0010] Preparation of Component B: The VOC content of Component B only needs to meet the requirements of this patent. During preparation, the filtration and packaging can be designed according to the specific formula.

[0011] Hydrophobically modified silica aerogels, including silica aerogels surface-modified with hexamethyldisilazane or trimethylchlorosilane.

[0012] The ceramic fiber is any one or more of aluminosilicate fiber, alumina fiber, and mullite fiber in any proportion, with a length of 0.5 mm to 3 mm.

[0013] Microspheres are closed-cell microspheres, which are one or more of glass microspheres, ceramic microspheres, cenospheres, and vacuum microspheres in any proportion.

[0014] The preservative and bactericide is any one or more of the following compounds: isozonones, formaldehyde-releasing compounds, benzimidazoles, substituted aromatic hydrocarbons, organic bromine compounds, organic amines, and triazines, in any proportion.

[0015] The dispersant is an anionic wetting and dispersing agent, including any one or more of carboxylates, sulfonates, sulfates, and phosphates in any proportion.

[0016] The defoamer is any one or more of mineral oil-based and organosilicon-based defoamers in any proportion.

[0017] This invention relates to a method for preparing a high-adhesion waterborne thermal insulation coating based on hydrophobic silica aerogel. By controlling the following six key points (control of waterborne epoxy emulsion dosage and VOC, control of waterborne epoxy curing agent dosage and VOC, dosage of hydrophobic silica aerogel, dosage of ceramic fiber, dosage of microspheres, and coating preparation process), the adhesion of the coating is improved while ensuring its thermal insulation performance. Attached Figure Description

[0018] Figure 1 The hydrophobic modified silica aerogel obtained in Example 1.

[0019] Figure 2 The hydrophobic modified silica aerogel obtained in Example 2. Detailed Implementation Example 1

[0020] Preparation of Component A: Under low-speed stirring, 75 kg of deionized water, 0.52 kg of preservative and bactericide, 0.15 kg of wetting agent, 3.1 kg of dispersant, and 0.78 kg of defoamer were added sequentially to a mixing tank and stirred for 5 minutes. Then, 13.5 kg of aerogel was slowly added, the stirring speed was increased to 400 rpm, and the mixture was dispersed for 60 minutes. The stirring speed was then reduced, and 3.1 kg of titanium dioxide and 31.4 kg of ceramic fiber were added and stirred for 25 minutes. Next, 82 kg of aqueous epoxy emulsion was slowly added and stirred until homogeneous. Then, 43 kg of microspheres and 1.26 kg of defoamer were added and stirred for 30 minutes. Finally, 3.8 kg of thickener was added and stirred for 20 minutes to obtain Component A. Component B was prepared in an amount of 60.52 kg. Example 2

[0021] Preparation of Component A: Under low-speed stirring, 145 kg of deionized water, 0.72 kg of preservative and bactericide, 0.38 kg of wetting agent, 4.5 kg of dispersant, and 1.55 kg of defoamer were added sequentially to a mixing tank and stirred for 5 minutes. Then, 22.0 kg of aerogel was slowly added, the stirring speed was increased to 400 rpm, and the mixture was dispersed for 60 minutes. After that, the stirring speed was reduced, and 11.0 kg of titanium dioxide and 54.5 kg of ceramic fiber were added and stirred for 25 minutes. Then, 126 kg of aqueous epoxy emulsion was slowly added and stirred evenly. Next, 67 kg of microspheres and 2.3 kg of defoamer were added and stirred for 30 minutes. Finally, 5.4 kg of thickener was added and stirred for 20 minutes to obtain Component A. The amount of Component B is 88.89 kg. Example 3

[0022] Preparation of Component A: Under low-speed stirring, 180 kg of deionized water, 0.9 kg of preservative and bactericide, 0.45 kg of wetting agent, 5.8 kg of dispersant, and 1.80 kg of defoamer were added sequentially to a mixing tank and stirred for 5 minutes. Then, 29.6 kg of aerogel was slowly added, the stirring speed was increased to 400 rpm, and the mixture was dispersed for 60 minutes. The stirring speed was then reduced, and 14 kg of titanium dioxide and 67 kg of ceramic fiber were added and stirred for 25 minutes. Next, 155 kg of aqueous epoxy emulsion was slowly added and stirred until homogeneous. Then, 83 kg of microspheres and 2.6 kg of defoamer were added and stirred for 30 minutes. Finally, 7.4 kg of thickener was added and stirred for 20 minutes to obtain Component A. Component B was prepared in an amount of 118.36 kg.

[0023] The products from Examples 1-3 were used to formulate paints, and the adhesion of the coatings was tested after 14 days of drying. The results are as follows:

Claims

1. A high-adhesion waterborne thermal insulation coating prepared based on hydrophobic silica aerogel, characterized in that: It consists of component A and component B. Mix thoroughly before use. Component A is formulated as follows by mass percentage: Deionized water 25.0%~38.0% Preservative and bactericide: 0.15%–0.20% Wetting agent 0.05%~0.1% Dispersant 1.0%–1.2% Defoamer 0.2%–0.4% Aerogel 4.0%–6.0% Titanium dioxide 1.0%~3.0% Ceramic fiber 10.0%~14.0% Waterborne epoxy emulsion 28.0%–32.0% Microbeads 15%–17% Defoamer 0.4%–0.6% Thickener 1.2%–1.5% The formulation of component B, by mass percentage, is as follows: 100% water-based epoxy curing agent The ratio of epoxy group content in component A to active hydrogen content in component B (curing agent) is 100:80-100.

2. The water-based heat-insulating coating according to claim 1, characterized in that: The cosolvent content of the aqueous epoxy emulsion described in component A must be less than 10 g / L. It can be a commercially available aqueous epoxy emulsion or it can be produced through reprocessing. If the VOC content of the commercially available aqueous epoxy emulsion is higher than 10 g / L, the VOC content can be reduced to below 10 g / L through vacuum removal, steam stripping, and membrane separation technology.

3. The water-based heat-insulating coating according to claim 1, characterized in that: The co-solvent content of the waterborne epoxy curing agent described in component B must be less than 10 g / L. It can be a commercially available waterborne epoxy curing agent or it can be produced through reprocessing. If the VOC content of the commercially available waterborne epoxy curing agent is higher than 10 g / L, the VOC content can be reduced to below 10 g / L through vacuum removal, steam stripping, and membrane separation technology.

4. The water-based heat-insulating coating according to claim 1, characterized in that: The aerogel is a hydrophobically modified silica aerogel, including silica aerogels surface-modified with hexamethyldisilazane or trimethylchlorosilane.

5. The water-based heat-insulating coating according to claim 1, characterized in that: The ceramic fiber is any one or a mixture of two or more of aluminosilicate fiber, alumina fiber, and mullite fiber in any proportion, with a length of 0.5 mm to 3 mm.

6. The water-based heat-insulating coating according to claim 1, characterized in that: The microspheres are closed-cell microspheres, which are one or more of glass microspheres, ceramic microspheres, cenospheres, and vacuum microspheres in any proportion.

7. The water-based heat-insulating coating according to claim 1, characterized in that: The preservative and bactericide is any one or a mixture of two or more of the following: isozonones, formaldehyde-releasing compounds, benzimidazoles, substituted aromatic hydrocarbons, organic bromines, organic amines, and triazines, in any proportion.

8. The water-based heat-insulating coating according to claim 1, characterized in that: The dispersant is an anionic wetting and dispersing agent, including any one or more of carboxylates, sulfonates, sulfates, and phosphates in any proportion.

9. The water-based heat-insulating coating according to claim 1, characterized in that: The defoamer is any one or a mixture of two or more mineral oil-based or organosilicon-based defoamers in any proportion.

10. The method for preparing the water-based heat-insulating coating according to claim 1, characterized in that: Preparation of Component A: Under low-speed stirring, deionized water, preservative, wetting agent, dispersant, and defoamer are added sequentially to the mixing tank and stirred for 5 minutes. Then, aerogel is slowly sprinkled in, and the speed is increased to disperse for 60 minutes. After that, the speed is reduced, titanium dioxide and ceramic fiber are added and stirred for 25 minutes. Then, water-based epoxy emulsion is slowly added and stirred evenly. Microbeads and defoamer are added and stirred for 30 minutes. Finally, thickener is added and stirred for 20 minutes to obtain Component A. Preparation of Component B: The VOC content of Component B only needs to meet the requirements. During preparation, the filtration and packaging should be designed according to the specific formula.

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