An infrared-reflective paint and a method for preparing the same

Abstract

The application discloses an infrared reflective paint, and raw materials thereof include, by weight, 75-80 parts of polyurethane water emulsion and 20-25 parts of modified zinc oxide; wherein, in the preparation process of the modified zinc oxide, mercaptopropyl trimethoxysilane modified zinc oxide is subjected to oxidation reaction with an oxidizing agent, solid-liquid separation is conducted, and negatively charged zinc oxide particles are obtained; the negatively charged zinc oxide particles are uniformly mixed with a zinc salt aqueous solution, and then are left to stand, subjected to solid-liquid separation, dried, and calcined to obtain intermediate particles; the intermediate particles are subjected to graft modification with a silane coupling agent containing an epoxy group to obtain the modified zinc oxide. The application further discloses a preparation method of the infrared reflective paint. The infrared reflective paint has good infrared reflective heat insulation performance and stain resistance.

Description

Technical Field

[0001] This invention relates to the field of paint technology, and in particular to an infrared reflective paint and its preparation method. Background Technology

[0002] Sunlight's energy consists of three parts: ultraviolet light, visible light, and near-infrared light, accounting for 5%, 43%, and 52%, respectively. Infrared radiation is the primary heat source, with the vast majority of its energy transferred to building surfaces, leading to excessively high surface temperatures. Currently, infrared-reflective paint is commonly used to reduce building surface temperatures. However, because infrared-reflective heat-insulating paint is constantly exposed to the external environment, its stain resistance is low. Complex environmental factors such as rain, dust accumulation, and sunlight exposure can damage the paint's optical properties, reducing its reflective heat-insulating performance and preventing the maintenance of a stable, long-term reflective heat-insulating effect. Summary of the Invention

[0003] Based on the technical problems existing in the background technology, the present invention proposes an infrared reflective paint and its preparation method. The present invention has good infrared reflective heat insulation performance and anti-fouling performance.

[0004] This invention proposes an infrared reflective paint, the raw materials of which, by weight, include: 75-80 parts of polyurethane water emulsion and 20-25 parts of modified zinc oxide;

[0005] In the preparation of modified zinc oxide, mercaptopropyltrimethoxysilane-modified zinc oxide is oxidized with an oxidant, and then separated into solid and liquid phases to obtain negatively charged zinc oxide particles. The negatively charged zinc oxide particles are mixed with a zinc salt aqueous solution, allowed to stand, separated into solid and liquid phases, dried, and calcined to obtain intermediate particles. The intermediate particles are then grafted with a silane coupling agent containing epoxy groups to obtain modified zinc oxide.

[0006] Preferably, in the preparation of modified zinc oxide, the particle size of mercaptopropyltrimethoxysilane-modified zinc oxide is 5-15 μm.

[0007] Zinc oxide possesses excellent infrared reflective and heat-insulating properties, but it is prone to agglomeration and difficult to disperse in paint, affecting the mechanical properties and infrared reflective and heat-insulating performance of the paint film. This invention involves oxidizing micron-sized mercaptopropyltrimethoxysilane-modified zinc oxide, transforming the mercapto groups into sulfonic acid groups with a negative charge, and then reacting them with Zn... 2+Electrostatic assembly followed by calcination generates nano-sized zinc oxide on the surface of micron-sized zinc oxide, forming micro-nano structures (i.e., intermediate particles). These intermediate particles are then grafted with a silane coupling agent containing epoxy groups to obtain modified zinc oxide, which improves its dispersibility in polyurethane, thereby enhancing the mechanical properties and infrared reflection and heat insulation performance of the coating film. Furthermore, the micro-nano structure of the modified zinc oxide can improve the anti-fouling performance of the coating film, thus maintaining its infrared reflection and heat insulation performance for a long time.

[0008] The aforementioned silane coupling agents containing epoxy groups can be γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, 3-(2,3-epoxypropoxy)propylmethyldimethoxysilane, etc.

[0009] Preferably, in the preparation of modified zinc oxide, the oxidant is an aqueous solution of hydrogen peroxide with a mass fraction of 10-20 wt%.

[0010] The amount of hydrogen peroxide solution used is not limited, as long as it can convert the thiol groups into sulfonic acid groups.

[0011] Preferably, in the preparation of modified zinc oxide, the oxidation reaction temperature is 35-45℃ and the time is 1-1.5h.

[0012] Preferably, in the preparation of modified zinc oxide, the zinc salt is an inorganic zinc salt. The inorganic zinc salt can be zinc chloride, etc.

[0013] Preferably, during the preparation of modified zinc oxide, the pH of the zinc salt aqueous solution is 3-4.

[0014] The amount of zinc salt solution used is not limited, which allows negatively charged zinc oxide particles to uniformly adsorb Zn. 2+ That's all.

[0015] Preferably, the modified zinc oxide is left to stand for 8-10 hours during preparation.

[0016] Preferably, in the preparation of modified zinc oxide, the calcination temperature is 500-600℃ and the time is 2-3h.

[0017] Preferably, the raw materials for synthesizing the polyurethane aqueous emulsion are: diisocyanate, polyether polyol, dimethylolpropionic acid, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, 1,3,5-tris(4-aminophenoxy)benzene, and catalyst.

[0018] This invention uses N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane as a synthetic raw material, introducing silane into polyurethane to improve the hydrophobic properties of the coating film, and further improving the antifouling properties of the coating film by working in conjunction with modified zinc oxide.

[0019] This invention uses 1,3,5-tris(4-aminophenoxy)benzene as a synthetic raw material, introducing active amino groups into the polyurethane. These amino groups react with the epoxy groups on the surface of modified zinc oxide, causing the zinc oxide to connect with the polyurethane molecular chains, promoting the uniform dispersion of the modified zinc oxide, and further improving the mechanical properties, infrared reflection heat insulation properties, and anti-fouling properties of the paint film. Furthermore, the introduction of 1,3,5-tris(4-aminophenoxy)benzene can form a cross-linked network, further improving the mechanical properties of the paint film.

[0020] Preferably, the diisocyanate is a polyphenyl polymethylene polyisocyanate.

[0021] Preferably, the polyether polyol is polyether diol 2000.

[0022] Preferably, the weight ratio of diisocyanate, polyether polyol, dimethylolpropionic acid, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, 1,3,5-tris(4-aminophenoxy)benzene, and catalyst is 45-50:40-45:3-4:1-3:1-3:0.01-0.05.

[0023] Preferably, in the preparation of the polyurethane aqueous emulsion, polyether polyol, dimethylolpropionic acid, and catalyst are mixed, and diisocyanate is added in an inert gas atmosphere to carry out the reaction. Organic solvent and N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane are added to continue the reaction. The pH is adjusted to neutral, and 1,3,5-tris(4-aminophenoxy)benzene is added to continue the reaction. Water is added for emulsification, and the organic solvent is removed to obtain the polyurethane aqueous emulsion.

[0024] Preferably, diisocyanate is added during the preparation of the polyurethane aqueous emulsion, and the reaction is carried out at 70-80°C for 3-4 hours.

[0025] Preferably, during the preparation of the polyurethane aqueous emulsion, an organic solvent and N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane are added and the reaction continues for 20-30 minutes.

[0026] Preferably, during the preparation of the polyurethane aqueous emulsion, 1,3,5-tris(4-aminophenoxy)benzene is added and the reaction continues for 20-30 minutes.

[0027] Preferably, acetone is used as the organic solvent in the preparation of the polyurethane aqueous emulsion.

[0028] Preferably, the pH is adjusted to neutral using triethylamine.

[0029] Preferably, the solid content of the polyurethane emulsion is 60-65 wt%.

[0030] The raw materials for the aforementioned infrared reflective paint may also include: dispersants, leveling agents, defoamers, antifreeze agents, etc.

[0031] The present invention also discloses a method for preparing the above-mentioned infrared reflective paint, comprising the following steps: mixing polyurethane aqueous emulsion and modified zinc oxide to obtain infrared reflective paint.

[0032] Beneficial effects:

[0033] This invention involves oxidizing micron-sized mercaptopropyltrimethoxysilane-modified zinc oxide to convert the mercapto groups into sulfonic acid groups, which carry a negative charge, and then reacting them with Zn. 2+ Electrostatic assembly followed by calcination generates nano-sized zinc oxide on the surface of micron-sized zinc oxide, forming micro-nano structures (i.e., intermediate particles). These intermediate particles are then grafted with a silane coupling agent containing epoxy groups to obtain modified zinc oxide, which improves its dispersibility in polyurethane, thereby enhancing the mechanical properties and infrared reflection and heat insulation performance of the coating film. Furthermore, the micro-nano structure of the modified zinc oxide can improve the anti-fouling performance of the coating film, thus maintaining its infrared reflection and heat insulation performance for a long time.

[0034] This invention uses N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane as a synthetic raw material, introducing silane into polyurethane to improve the hydrophobic properties of the coating film, and further improving the antifouling properties of the coating film by working in conjunction with modified zinc oxide.

[0035] This invention uses 1,3,5-tris(4-aminophenoxy)benzene as a synthetic raw material, introducing active amino groups into the polyurethane. These amino groups react with the epoxy groups on the surface of modified zinc oxide, causing the zinc oxide to connect with the polyurethane molecular chains, promoting the uniform dispersion of the modified zinc oxide, and further improving the mechanical properties, infrared reflection heat insulation properties, and anti-fouling properties of the paint film. Furthermore, the introduction of 1,3,5-tris(4-aminophenoxy)benzene can form a cross-linked network, further improving the mechanical properties of the paint film. Detailed Implementation

[0036] The technical solution of the present invention will be described in detail below through specific embodiments. However, it should be clearly stated that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention.

[0037] Example 1

[0038] An infrared reflective paint, the raw materials of which, by weight, include: 75 parts of polyurethane water emulsion, 25 parts of modified zinc oxide, and 2 parts of dispersant Coadis123K.

[0039] In the preparation of modified zinc oxide, mercaptopropyltrimethoxysilane modified zinc oxide with a particle size of 5 μm is mixed with a hydrogen peroxide aqueous solution with a mass fraction of 10 wt%, heated to 35 °C and stirred for 1.5 h for oxidation reaction, filtered, washed with water and dried to obtain negatively charged zinc oxide particles.

[0040] A negatively charged aqueous dispersion of zinc oxide particles was mixed with a 0.1 mol / L zinc chloride aqueous solution, the pH was adjusted to 4 with hydrochloric acid, and the mixture was allowed to stand for 10 h. After filtration, washing with water, and drying, the mixture was calcined at 500 °C for 3 h to obtain intermediate particles. The intermediate particles were added to a 5 wt% aqueous solution of γ-glycidyl etheroxypropyltrimethoxysilane ethanol, heated to 60 °C, stirred for 3 h, filtered, washed, and dried to obtain modified zinc oxide.

[0041] In the preparation of polyurethane aqueous emulsion, polyether diol 2000, dimethylolpropionic acid, and dibutyltin dilaurate were mixed and stirred. Under nitrogen protection, polyphenyl polymethylene polyisocyanate was added, and the mixture was heated to 70°C and reacted for 4 hours. Acetone was added to adjust the viscosity, and then N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane was added and the reaction was continued for 30 minutes. The pH was adjusted to neutral with triethylamine, and then 1,3,5-tris(4-aminophenoxy) The benzene reaction continued for 30 minutes, then water was added for shear emulsification, and then acetone was removed by vacuum evaporation to obtain a polyurethane aqueous emulsion with a solid content of 60 wt%. The weight ratio of polyphenyl polymethylene polyisocyanate, polyether diol 2000, dimethylolpropionic acid, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, 1,3,5-tris(4-aminophenoxy)benzene and dibutyltin dilaurate was 50:40:4:3:3:0.05.

[0042] The preparation method of the above-mentioned infrared reflective paint includes the following steps: mixing polyurethane water emulsion, modified zinc oxide, and dispersant Coadis123K to obtain infrared reflective paint.

[0043] Example 2

[0044] An infrared reflective paint, the raw materials of which, by weight, include: 80 parts of polyurethane water emulsion, 20 parts of modified zinc oxide, and 2 parts of dispersant Coadis123K;

[0045] In the preparation of modified zinc oxide, mercaptopropyltrimethoxysilane modified zinc oxide with a particle size of 15 μm is mixed with a hydrogen peroxide aqueous solution with a mass fraction of 20 wt%, heated to 45 °C and stirred for 1 h for oxidation reaction, filtered, washed with water and dried to obtain negatively charged zinc oxide particles.

[0046] A negatively charged aqueous dispersion of zinc oxide particles was mixed with a 0.1 mol / L zinc chloride aqueous solution, the pH was adjusted to 3 with hydrochloric acid, and the mixture was allowed to stand for 8 hours. After filtration, washing with water, and drying, the mixture was calcined at 600℃ for 2 hours to obtain intermediate particles. The intermediate particles were added to a 5 wt% aqueous solution of γ-glycidyl etheroxypropyltrimethoxysilane ethanol, heated to 60℃, stirred for 3 hours, filtered, washed, and dried to obtain modified zinc oxide.

[0047] In the preparation of polyurethane aqueous emulsion, polyether diol 2000, dimethylolpropionic acid, and dibutyltin dilaurate were mixed and stirred. Under nitrogen protection, polyphenyl polymethylene polyisocyanate was added, and the mixture was heated to 80°C and reacted for 3 hours. Acetone was added to adjust the viscosity, and then N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane was added and the reaction was continued for 20 minutes. The pH was adjusted to neutral with triethylamine, and then 1,3,5-tris(4-aminophenoxy) The benzene reaction continued for 20 minutes, then water was added for shear emulsification, and then acetone was removed by vacuum evaporation to obtain a polyurethane aqueous emulsion with a solid content of 65 wt%. The weight ratio of polyphenyl polymethylene polyisocyanate, polyether diol 2000, dimethylolpropionic acid, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, 1,3,5-tris(4-aminophenoxy)benzene and dibutyltin dilaurate was 50:45:3:1:1:0.05.

[0048] The preparation method of the above-mentioned infrared reflective paint includes the following steps: mixing polyurethane water emulsion, modified zinc oxide, and dispersant Coadis123K to obtain infrared reflective paint.

[0049] Example 3

[0050] An infrared reflective paint, the raw materials of which, by weight, include: 78 parts of polyurethane water emulsion, 22 parts of modified zinc oxide, and 2 parts of dispersant Coadis123K;

[0051] In the preparation of modified zinc oxide, mercaptopropyltrimethoxysilane modified zinc oxide with a particle size of 10 μm is mixed with a hydrogen peroxide aqueous solution with a mass fraction of 20 wt%, heated to 40 °C and stirred for 1.5 h for oxidation reaction, filtered, washed with water and dried to obtain negatively charged zinc oxide particles.

[0052] A negatively charged aqueous dispersion of zinc oxide particles was mixed with a 0.1 mol / L zinc chloride aqueous solution, the pH was adjusted to 3.5 with hydrochloric acid, and the mixture was allowed to stand for 9 hours. After filtration, washing with water, and drying, the mixture was calcined at 600℃ for 3 hours to obtain intermediate particles. The intermediate particles were added to a 5 wt% aqueous solution of γ-glycidyl etheroxypropyltrimethoxysilane ethanol, heated to 60℃, stirred for 3 hours, filtered, washed, and dried to obtain modified zinc oxide.

[0053] In the preparation of the polyurethane aqueous emulsion, polyether diol 2000, dimethylolpropionic acid, and dibutyltin dilaurate were mixed and stirred. Under nitrogen protection, polyphenyl polymethylene polyisocyanate was added, and the mixture was heated to 75°C and reacted for 3.5 h. Acetone was added to adjust the viscosity, and then N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane was added and the reaction was continued for 30 min. The pH was adjusted to neutral with triethylamine, and then 1,3,5-tris(4-aminophenoxy)benzene was added. The reaction was continued for 30 minutes, then water was added for shear emulsification, and then acetone was removed by vacuum evaporation to obtain a polyurethane aqueous emulsion with a solid content of 60 wt%. The weight ratio of polyphenyl polymethylene polyisocyanate, polyether diol 2000, dimethylolpropionic acid, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, 1,3,5-tris(4-aminophenoxy)benzene, and dibutyltin dilaurate was 48:43:4:2.5:2.5:0.05.

[0054] The preparation method of the above-mentioned infrared reflective paint includes the following steps: mixing polyurethane water emulsion, modified zinc oxide, and dispersant Coadis123K to obtain infrared reflective paint.

[0055] Comparative Example 1

[0056] Replace “modified zinc oxide” with “mercaptopropyltrimethoxysilane modified zinc oxide”, otherwise the same as in Example 3.

[0057] Comparative Example 2

[0058] Replace “modified zinc oxide” with “intermediate particles in Example 3”, otherwise the same as in Example 3.

[0059] Comparative Example 3

[0060] In the preparation of the polyurethane aqueous emulsion, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane is not included, and the rest is the same as in Example 3.

[0061] Comparative Example 4

[0062] In the preparation of the polyurethane aqueous emulsion, 1,3,5-tris(4-aminophenoxy)benzene is not included, and other aspects are the same as in Example 3.

[0063] The paints prepared in Examples 1-3 and Comparative Examples 1-4 were coated onto clean, rough steel plates and dried to obtain paint films with a thickness of approximately 20 μm. The various properties of the paint films were then tested. The results are shown in Table 1.

[0064] Thermal insulation temperature difference was tested according to JG / T235-2008. Pencil hardness was tested according to GB / T6739-2022. Adhesion was tested according to GB / T9286-2021, with the paint adhesion rated from level 0 (completely undamaged) to level 5 (severely damaged).

[0065] Table 1 Test Results

[0066] Testing items Thermal insulation temperature difference ℃ Water contact angle ° Pencil hardness Adhesion rating Example 1 8.0 162 3H 0 Example 2 7.6 159 3H 0 Example 3 7.9 161 3H 0 Comparative Example 1 7.9 91 3H 2 Comparative Example 2 7.7 105 3H 2 Comparative Example 3 7.9 99 2H 0 Comparative Example 4 7.7 160 2H 2

[0067] As can be seen from Table 1, compared with Comparative Examples 1-3, the paint film of the present invention has good infrared reflection and heat insulation properties, and the water contact angle is much larger than that of Comparative Examples 1-3. It has good anti-fouling properties, and the paint film of the present invention has good hardness and adhesion.

[0068] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. An infrared reflective paint characterized in that, The raw materials include, by weight parts: polyurethane water emulsion 75-80 parts, modified zinc oxide 20-25 parts; In the preparation of the modified zinc oxide, the mercaptopropyl trimethoxysilane modified zinc oxide is oxidized with an oxidizing agent, solid-liquid separation is performed, and negatively charged zinc oxide particles are obtained; the negatively charged zinc oxide particles are mixed with a zinc salt aqueous solution, left to stand, solid-liquid separation is performed, dried, and calcined to obtain intermediate particles; the intermediate particles are grafted and modified with a silane coupling agent containing an epoxy group to obtain the modified zinc oxide; In the preparation of the modified zinc oxide, the particle size of the mercaptopropyl trimethoxysilane modified zinc oxide is 5-15 μm. In the preparation of the modified zinc oxide, the calcination temperature is 500-600℃, and the time is 2-3 h. The raw materials for synthesizing the polyurethane water emulsion are: polyphenyl polymethylene polyisocyanate, polyether polyol, dimethylol propionic acid, N-β-(aminoethyl)-γ-aminopropyl trimethoxysilane, 1,3,5-tris(4-aminophenoxy) benzene, and a catalyst. The weight ratio of the polyphenyl polymethylene polyisocyanate, polyether polyol, dimethylol propionic acid, N-β-(aminoethyl)-γ-aminopropyl trimethoxysilane, 1,3,5-tris(4-aminophenoxy) benzene, and catalyst is 45-50:40-45:3-4:1-3:1-3:0.01-0.

05. In the preparation of the polyurethane water emulsion, the polyether polyol, dimethylol propionic acid, and catalyst are mixed, polyphenyl polymethylene polyisocyanate is added in an inert gas atmosphere, and reaction is performed; organic solvent and N-β-(aminoethyl)-γ-aminopropyl trimethoxysilane are added for continued reaction, the pH is adjusted to neutral, 1,3,5-tris(4-aminophenoxy) benzene is added for continued reaction, water is added for emulsification, and the organic solvent is removed to obtain the polyurethane water emulsion.

2. The infrared reflective paint of claim 1, wherein In the preparation of the modified zinc oxide, the oxidizing agent is a 10-20wt% hydrogen peroxide aqueous solution.

3. The infrared reflective paint of claim 1, wherein In the preparation of the modified zinc oxide, the temperature of the oxidation reaction is 35-45℃, and the time is 1-1.5 h.

4. The infrared reflective paint of claim 1, wherein In the preparation of the modified zinc oxide, the zinc salt is an inorganic zinc salt.

5. The infrared reflective paint of claim 1, wherein In the preparation of the modified zinc oxide, the pH of the zinc salt aqueous solution is 3-4.

6. The infrared reflective paint of claim 1, wherein In the preparation of the modified zinc oxide, the standing time is 8-10 h.

7. The infrared reflective paint of claim 1, wherein The polyether polyol is polyether diol 2000.

8. The infrared reflective paint of claim 1, wherein In the preparation of the polyurethane water emulsion, polyphenyl polymethylene polyisocyanate is added, and reaction is performed at 70-80℃ for 3-4 h.

9. The infrared reflective paint of claim 1, wherein In the preparation of the polyurethane water emulsion, organic solvent and N-β-(aminoethyl)-γ-aminopropyl trimethoxysilane are added for continued reaction for 20-30 min.

10. The infrared reflective paint of claim 1, wherein In the preparation of the polyurethane water emulsion, 1,3,5-tris(4-aminophenoxy) benzene is added for continued reaction for 20-30 min.

11. The infrared reflective paint of claim 1, wherein In the preparation of the polyurethane water emulsion, the organic solvent is acetone.

12. The infrared reflective paint of claim 1, wherein The pH is adjusted to neutral with triethylamine.

13. The infrared reflective paint of claim 1, wherein The solid content of the polyurethane water emulsion is 60-65wt%.

14. A process for the preparation of an infrared-reflective paint according to any one of claims 1 to 13, characterized in that, The method comprises the following steps: mixing the polyurethane water emulsion and the modified zinc oxide to obtain an infrared reflective paint.