Voc-free coating for daytime radiative cooling textiles and use thereof

Abstract

The application discloses a VOC-free coating for daytime radiative cooling textiles and application thereof, which is prepared by blending one or more organic silicon particles and / or inorganic particles with an aqueous polymer emulsion containing fluorinated acrylate polymer; the organic silicon particles are at least one of polymethyl trialkoxy microspheres, polyphenyl trialkoxy microspheres, polyvinyl trialkoxy microspheres, polyepoxy alkoxyl microspheres, polymethyl vinyl alkoxyl microspheres and polymethyl phenyl alkoxyl microspheres; the inorganic particles are at least one of silicon dioxide, titanium dioxide, zinc oxide and aluminum phosphate; the particle size of the organic silicon particles and / or inorganic particles is 0.5-10 mu m. The textile finished by the VOC-free coating has good daytime radiative cooling effect and washing fastness.

Description

Technical Field

[0001] This invention relates to the field of daytime radiation cooling technology, and more particularly to a VOC-free coating for daytime radiation cooling textiles and its application. Background Technology

[0002] With population growth, rapid industrialization, and societal development, the energy demand for air conditioning has reached unprecedented levels, accelerating global warming. Notably, the refrigerants used in air conditioning are one of the biggest contributors to global warming. Radiant cooling, as a passive cooling solution, holds promise as a green technology that effectively reduces energy consumption without any electricity input or greenhouse gas emissions.

[0003] Passive daytime radiative cooling (PDRC) materials radiate heat into outer space through atmospheric windows in the 8-13 μm infrared band. However, direct sunlight and non-radiative heat from the environment pose significant challenges to daytime radiative cooling. Recent research has achieved breakthroughs in daytime radiative cooling by utilizing specialized structures and materials, such as photonic structural materials, multilayer structures, metallic dielectric systems, and metamaterials. However, these structures and materials are neither cost-effective nor scalable.

[0004] To facilitate the implementation of large-scale radiative cooling, scalable polymer-based materials tailored for daytime radiative cooling have been developed, such as P(VdF-HFP) and PTFE, which are used in PDRC due to the overlap of their inherent vibrational frequencies with atmospheric windows (8-13 μm). Phase inversion methods have received increasing attention, and polymer-based daytime radiative cooling coatings are at the forefront of development due to their potential for large-scale application in buildings. However, phase inversion methods typically involve significant VOC emissions, causing environmental pollution and serious health problems. Therefore, creating high-performance radiative cooling coatings remains a challenging task.

[0005] Patent application publication number CN 116836592 A discloses a method for preparing a radiation-cooling coating, characterized by comprising: 10 parts of reflective filler, 10 parts of fluorescent filler, 10 parts of film-forming material, and 50 parts of organic solvent. The polysiloxane resin and silica in the radiation-cooling coating prepared by this method possess a large number of silicon-oxygen bonds, exhibiting excellent emissivity in the 8-14 μm wavelength range. However, the use of the organic solvent 200# solvent oil will have certain negative environmental impacts.

[0006] Patent application publication number CN 114016300 A discloses a coated textile with passive radiative cooling function and its preparation method. This method effectively increases the reflectivity of sunlight by constructing a polymer hierarchical porous structure on the surface of the textile, thereby improving its radiative cooling effect. Furthermore, the coated textile possesses UV resistance and hydrophobicity. However, the use of acetone during the polymer dissolution process still causes environmental pollution, which contradicts the construction of an environmentally friendly society. Summary of the Invention

[0007] This invention provides a VOC-free coating for daytime radiative cooling textiles. Textiles treated with this VOC-free coating have good daytime radiative cooling effect and wash fastness.

[0008] The technical solution of the present invention is as follows:

[0009] A VOC-free coating for daytime radiative cooling textiles is made by blending one or more organosilicon particles and / or inorganic particles with an aqueous polymer emulsion containing fluorinated acrylate polymers.

[0010] The organosilicon particles are at least one of polymethyltrialkoxy microspheres, polyphenyltrialkoxy microspheres, polyvinyltrialkoxy microspheres, polyepoxyalkoxy microspheres, polymethylvinylalkoxy microspheres, and polymethylphenylalkoxy microspheres.

[0011] The inorganic particles are at least one of silicon dioxide, titanium dioxide, zinc oxide, and aluminum phosphate;

[0012] The particle size of the organosilicon particles and / or inorganic particles is 0.5-10 μm.

[0013] Fabrics treated with the VOC-free coating of this invention have good daytime radiative cooling effect and excellent wash fastness. Even after multiple washes, the fabric still has a good daytime radiative cooling effect.

[0014] When selecting a water-based polymer emulsion, the first consideration should be the adhesion performance between the polymer and the substrate to ensure the strong adhesion between the coating and the substrate; the second consideration should be the influence of the transparency of the polymer before and after film formation on the spectral properties of the added particles; and finally, the weather resistance of the polymer should be considered.

[0015] Preferably, the fluorinated acrylate polymer is obtained by emulsion polymerization of butyl acrylate, methyl methacrylate, and 2-perfluorobutylethyl acrylate in water.

[0016] Preferably, the aqueous polymer emulsion is obtained by emulsion polymerization of the following raw materials in the indicated mass fractions:

[0017]

[0018] The above-mentioned aqueous polymer emulsion is obtained through emulsion polymerization, contains no VOC solvents, and is environmentally friendly. In the above-mentioned aqueous polymer emulsion, the fluorinated acrylate polymer obtained by polymerization has CF bonds, and the emissivity of the polymer after film formation is higher than that of pure acrylate polymer, which makes the coating have a better daytime radiation cooling effect, and the fluorinated acrylate polymer has good adhesion to the fabric substrate. The fluorinated acrylate polymer has high transparency and has virtually no impact on the spectral properties of organosilicon particles and / or inorganic particles.

[0019] More preferably, the aqueous polymer emulsion is obtained by emulsion polymerization of the following raw materials in the indicated mass fractions:

[0020]

[0021] The auxiliary agent is an initiator. Most preferably, the auxiliary agent is azobisisobutyronitrile (AIBN); the surfactant is 1-allyloxy-3-(4-nonylphenol)-2-propanol polyoxyethylene (10) ether ammonium sulfate (DNS-86).

[0022] A further preferred method for preparing the aqueous polymer emulsion includes: mixing and emulsifying the raw materials to obtain a pre-emulsion; polymerizing the pre-emulsion at 70-100℃ for 1-10 hours under an inert atmosphere to obtain an aqueous polymer emulsion containing fluorinated acrylate polymer.

[0023] The organosilicon particles can be prepared using existing technologies.

[0024] Preferably, the method for preparing the organosilicon particles includes:

[0025] (a) Mix organosilicon monomer with water, add additive A to form a reaction solution, and react at 15-50°C for 2-10 hours; the additive A is an acid;

[0026] (b) Adding auxiliary agent B to the reaction mixture of step (a), and reacting for 0.01 to 0.5 h to obtain a suspension of organosilicon microsphere material; wherein the auxiliary agent B is an alkali;

[0027] (c) Separate and dry the suspension of the organosilicon microsphere material from step (b) to obtain the organosilicon microsphere material;

[0028] The organosilicon monomer is a trialkoxysilane, including at least one of methyltrimethoxysilane, methyltriethoxysilane, aminotrimethoxysilane, aminotriethoxysilane, epoxytrimethoxysilane, and epoxytriethoxysilane.

[0029] The surface of the organosilicon particles has a large number of nanoscale papillae. These nanopapillae can enhance the reflectivity of the organosilicon particles in the solar spectrum range through Rayleigh scattering. When the organosilicon particles are mixed with an aqueous polymer emulsion to form a coating and then applied to the surface of textiles, the nanopapillae structure on the surface of the organosilicon particles does not change.

[0030] Preferably, the particle size of the organosilicon particles and / or inorganic particles is 0.5-1 μm.

[0031] Preferably, in the total amount of organosilicon particles and / or inorganic particles and fluorinated acrylate polymer, the mass fraction of organosilicon particles and / or inorganic particles is 70-95%, and the mass fraction of fluorinated acrylate polymer is 5-30%.

[0032] As the mass fraction of organosilicon particles and / or inorganic particles in VOC-free coatings increases, the reflectivity of the coating material also increases, but the bonding strength between organosilicon particles and / or inorganic particles and textiles gradually decreases.

[0033] More preferably, in the total amount of organosilicon particles and / or inorganic particles and fluorinated acrylate polymer, the mass fraction of organosilicon particles and / or inorganic particles is 85-95%, and the mass fraction of fluorinated acrylate polymer is 5-15%.

[0034] This invention prepares a VOC-free coating for daytime radiation cooling through a simple physical mixing method. This VOC-free coating can be applied to the surface of textiles to obtain a daytime radiation cooling coating.

[0035] The VOC-free coating of this invention can be prepared and used immediately.

[0036] The present invention also provides a textile with a daytime radiation cooling coating, which is prepared by the following method: applying the VOC-free coating to the surface of the textile and drying it to obtain the textile with the daytime radiation cooling coating.

[0037] The process of applying the VOC-free coating to textiles includes immersing the prepared textiles in the VOC-free coating to form an organic / inorganic particle material coating with daytime radiative cooling effect.

[0038] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0039] (1) The emulsion used in the VOC-free coating of daytime radiation cooling textiles of the present invention is prepared by emulsion polymerization. The preparation process is simple and easy to operate. The solvent is water and no organic solvent is used, which is green and environmentally friendly.

[0040] (2) The method for preparing the VOC-free coating for daytime radiation cooling textiles of the present invention is simple and easy to implement, and can be obtained by a simple physical mixing method;

[0041] (3) Fluorinated acrylate polymers have CF bonds, and the polymer has high emissivity after film formation, which makes the coating have a good daytime radiation cooling effect. In addition, fluorinated acrylate polymers have high transparency and have little effect on the spectral properties of organosilicon particles and / or inorganic particles.

[0042] (4) Fluorinated acrylate polymers have good adhesion to the fabric substrate, and fabrics treated with this VOC-free coating have excellent wash fastness. Attached Figure Description

[0043] Figure 1 The image shows the reflectance data of the VOC-free coated textile prepared in Example 3 in the ultraviolet-visible-near-infrared spectral range.

[0044] Figure 2 This is a graph showing the emissivity data in the mid-infrared spectral range of the VOC-free coated textile prepared in Example 3.

[0045] Figure 3 The image shown is a scanning electron microscope image of the VOC-free coated textile prepared in Example 7.

[0046] Figure 4 The temperature changes of the VOC-free coated textile prepared in Example 7 and the textile without VOC coating under outdoor solar radiation.

[0047] Figure 5 The temperature changes of the VOC-free coated textile prepared in Example 7 under outdoor solar radiation after 25 commercial washes, compared with those of textiles without VOC coating. Detailed Implementation

[0048] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be noted that the embodiments described below are intended to facilitate the understanding of the present invention and do not limit it in any way.

[0049] In the following embodiments, to achieve the application of VOC-free coatings on textiles: the prepared textiles are immersed in VOC-free coatings to form a VOC-free coating with daytime radiative cooling effect. The sample is then subjected to UV-Vis-NIR reflectance and infrared emissivity tests, and the reflectance and emissivity of the sample are calculated.

[0050] In the following examples, the particle size of the organosilicon microspheres and silica microspheres is 500-1000 nm.

[0051] Example 1

[0052] Preparation of fluorinated acrylate emulsions:

[0053] 1) Add 0.48 g of initiator azobisisobutyronitrile (AIBN), 1.28 g of 1-allyloxy-3-(4-nonylphenol)-2-propanol polyoxyethylene (10) ether ammonium sulfate (DNS-86), 8.0 g of methyl methacrylate (MMA), 8.0 g of 2-perfluorobutyl ethyl acrylate (TEAC-4), 16.0 g of butyl acrylate (BA), and 128 g of deionized water to a 500 mL beaker. After complete emulsification, homogenize in a homogenizer. After 30 min, a pre-emulsion is obtained.

[0054] 2) Pour the above pre-emulsion into a four-necked flask equipped with a stirrer, thermometer and condenser, purge with high-purity nitrogen for 30 minutes to remove air, and continue polymerization for 4 hours under constant temperature water bath at 80℃ to obtain fluorinated acrylate emulsion.

[0055] Example 2

[0056] Preparation of organosilicon microspheres:

[0057] Mix 1.5 g of methyltrimethoxysilane with 40 g of water until homogeneous, then add 0.02 g of glacial acetic acid. Stir and hydrolyze in an oil bath at 20 °C for 8 h. Add 0.04 g of ammonia to the mixture and react for 5 min to obtain an organosilicon microsphere suspension.

[0058] Example 3

[0059] 1) Weigh 12.5 g of organosilicon microsphere suspension with a solid content of 20% and add it to 2.5 g of fluorinated acrylate emulsion with a solid content of 20%, stir evenly to obtain VOC-free coating.

[0060] 2) Immerse the prepared textile in the VOC-free coating of step 1), remove and dry it to form an organosilicon microsphere material coating with daytime radiation cooling effect on the surface of the textile.

[0061] Example 4

[0062] 1) Weigh 15.0 g of organosilicon microsphere suspension with a solid content of 20% and add it to 2.5 g of fluorinated acrylate emulsion with a solid content of 20%, stir evenly to obtain VOC-free coating.

[0063] 2) Immerse the prepared textile in the VOC-free coating of step 1), remove and dry it to form an organosilicon microsphere material coating with daytime radiation cooling effect on the surface of the textile.

[0064] Example 5

[0065] 1) Weigh 17.5 g of organosilicon microsphere suspension with a solid content of 20% and add it to 2.5 g of fluorinated acrylate emulsion with a solid content of 20%, stir evenly to obtain VOC-free coating.

[0066] 2) Immerse the prepared textile in the VOC-free coating of step 1), remove and dry it to form an organosilicon microsphere material coating with daytime radiation cooling effect on the surface of the textile.

[0067] Example 6

[0068] 1) Weigh 20.0 g of organosilicon microsphere suspension with a solid content of 20% and add it to 2.5 g of fluorinated acrylate emulsion with a solid content of 20%, stir evenly to obtain VOC-free coating.

[0069] 2) Immerse the prepared textile in the VOC-free coating of step 1), remove and dry it to form an organosilicon microsphere material coating with daytime radiation cooling effect on the surface of the textile.

[0070] Example 7

[0071] 1) Weigh 22.5g of organosilicon microsphere suspension with a solid content of 20% and add it to 2.5g of fluorinated acrylate emulsion with a solid content of 20%, stir evenly to obtain VOC-free coating.

[0072] 2) Immerse the prepared textile in the VOC-free coating of step 1), remove and dry it to form an organosilicon microsphere material coating with daytime radiation cooling effect on the surface of the textile.

[0073] Example 8

[0074] 1) Weigh 35.0 g of organosilicon microsphere suspension with a solid content of 20% and add it to 2.5 g of fluorinated acrylate emulsion with a solid content of 20%, stir evenly to obtain VOC-free coating.

[0075] 2) Immerse the prepared textile in the VOC-free coating of step 1), remove and dry it to form an organosilicon microsphere material coating with daytime radiation cooling effect on the surface of the textile.

[0076] Example 9

[0077] 1) Weigh 47.5 g of organosilicon microsphere suspension with a solid content of 20% and add it to 2.5 g of fluorinated acrylate emulsion with a solid content of 20%, stir evenly to obtain VOC-free coating.

[0078] 2) Immerse the prepared textile in the VOC-free coating of step 1), remove and dry it to form an organosilicon microsphere material coating with daytime radiation cooling effect on the surface of the textile.

[0079] Example 10

[0080] 1) Weigh 22.5g of silica microsphere suspension with a solid content of 20% and add it to 2.5g of fluorinated acrylate emulsion with a solid content of 20%, stir evenly to obtain VOC-free coating.

[0081] 2) Immerse the prepared textile in the VOC-free coating of step 1), remove and dry it to form a silica microsphere material coating with daytime radiation cooling effect on the surface of the textile.

[0082] The textiles coated with organosilicon microspheres obtained in Examples 3-10 were subjected to ultraviolet-visible-near-infrared reflectance and mid-infrared emissivity tests. The test results are shown in Table 1.

[0083] Table 1. Test results of reflectance and emissivity in the solar and mid-infrared spectral ranges for Examples 3-10.

[0084]

[0085]

[0086] As shown in Table 1, the reflectivity increases with the increase of the proportion of organosilicon microspheres in VOC-free coatings.

[0087] Example 11

[0088] The textile with a VOC-free coating prepared in Example 7 was placed under outdoor solar radiation, and its cooling effect was measured. The results are as follows: Figure 4 As shown, the cooling effect of textiles with VOC-free coatings on their surfaces was compared with that of textiles without VOC-free coatings under the same outdoor environment. Figure 4 As can be seen, the temperature of textiles without VOC-free coatings reaches as high as 55℃, while the temperature of textiles with VOC-free coatings is around 37℃, a difference of 18℃. This indicates that textiles with VOC-free coatings have a significant cooling effect.

[0089] Example 12

[0090] After 25 commercial wash tests on the textile with VOC-free coating in Example 7, the coated textile still achieved a temperature 5°C lower than the untreated textile.

[0091] Figure 1 The image shows the reflectance data of the VOC-free coated textile prepared in Example 3 in the ultraviolet-visible-near-infrared spectral range. After calculation, the average reflectance of the VOC-free coated textile prepared in Example 3 in the solar spectral range (0.3-2.5μm) is 80%.

[0092] Figure 2The image shows the emissivity data in the mid-infrared spectral range of the VOC-free coated textile prepared in Example 3. Calculations show that the average emissivity of the VOC-free coated textile prepared in Example 3 within the atmospheric window (8-13 μm) is 88%.

[0093] Figure 3 The image shows a scanning electron microscope (SEM) image of the VOC-free coated textile prepared in Example 7. It can be seen from the image that the silicone microspheres on the textile are adhered to each other, and the papillae on the surface of the silicone microspheres are still clearly visible.

[0094] Figure 4 The figure shows the temperature changes of the VOC-free coated textile prepared in Example 7 and the textile without a VOC-free coating under outdoor solar radiation. As can be seen from the figure, the temperature of the textile without the VOC-free coating reaches as high as 55°C, while the temperature of the textile with the VOC-free coating is around 37°C, a difference of 18°C. This indicates that the textile with the VOC-free coating has a significant cooling effect.

[0095] The embodiments described above provide a detailed explanation of the technical solutions and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, additions, and equivalent substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A textile with a daytime radiation cooling coating, characterized in that, The VOC-free coating is prepared by applying a VOC-free coating to the surface of a textile and drying it to obtain a textile with a daytime radiation cooling coating. The VOC-free coating is prepared by blending one or more organosilicon particles and / or inorganic particles with an aqueous polymer emulsion containing fluorinated acrylate polymers. In the total amount of organosilicon particles and / or inorganic particles and fluorinated acrylate polymers, the mass fraction of organosilicon particles and / or inorganic particles is 70-95%, and the mass fraction of fluorinated acrylate polymers is 5-30%. The aqueous polymer emulsion is obtained by emulsion polymerization of the following raw materials in the indicated mass fractions: Butyl acrylate 5-15%; 1-5% methyl methacrylate; 1-5% of 2-perfluorobutyl ethyl acrylate; Surfactant 0.1-1%; Additives 0.1-0.5%; The remainder is water; The aforementioned additive is an initiator; the aforementioned surfactant is 1-allyloxy-3-(4-nonylphenol)-2-propanol polyoxyethylene (10) ether ammonium sulfate; The organosilicon particles are polymethyltrialkoxy microspheres or polyepoxyalkoxy microspheres; The inorganic particles are silica microspheres; The particle size of the organosilicon particles and / or inorganic particles is 0.5-1 μm.

2. The textile with a daytime radiation cooling coating according to claim 1, characterized in that, The preparation method of the aqueous polymer emulsion includes: mixing and emulsifying the raw materials to obtain a pre-emulsion; polymerizing the pre-emulsion at 70-100℃ for 1-10h under an inert atmosphere to obtain an aqueous polymer emulsion containing fluorinated acrylate polymer.

3. The textile with a daytime radiation cooling coating according to claim 1, characterized in that, The method for preparing the organosilicon particles includes: (a) Mix organosilicon monomer with water, add additive A to form a reaction solution, and react at 15~50℃ for 2~10h; the additive A is an acid; (b) Adding auxiliary agent B to the reaction mixture of step (a), and reacting for 0.01~0.5h to obtain a suspension of organosilicon microsphere material; wherein the auxiliary agent B is an alkali; (c) Separate and dry the suspension of the organosilicon microsphere material from step (b) to obtain the organosilicon microsphere material; The organosilicon monomer is at least one of methyltrimethoxysilane, methyltriethoxysilane, epoxytrimethoxysilane, and epoxytriethoxysilane.

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