Water-based modified resin, preparation method thereof and water-based radiation cooling coating

Abstract

The invention relates to a water-based modified resin and a preparation method thereof, and a water-based radiation cooling coating, the preparation method comprises the following steps: adding a mixed solution of an acrylic monomer and an initiator into propylene glycol monomethyl ether in batches, and carrying out a first reaction to obtain a hydroxy acrylic prepolymer; respectively and sequentially adding hydroxyl-terminated polydimethylsiloxane and isophorone diisocyanate into the hydroxyl acrylic acid prepolymer, carrying out a second reaction, and neutralizing after the reaction is finished, so as to obtain the water-based modified resin. The water-based modified resin disclosed by the invention is obvious in radiation cooling effect and high in adaptability, and can be widely applied to radiation cooling products such as water-based radiation cooling coatings and the like.

Description

Technical Field

[0001] The invention relates to the technical field of radiation cooling coatings, and in particular to a water-based modified resin and a preparation method thereof, and a water-based radiation cooling coating. Background Art

[0002] Radiative cooling technology is a zero-energy cooling technology with no energy input. The cooling principle of radiative cooling coatings comes from two aspects. On the one hand, the coating has a higher reflectivity in the sunlight band (0.3μm-2.5μm), reducing the temperature rise due to the absorption of solar radiation; on the other hand, the coating has a higher emissivity in the atmospheric window (8μm-13μm), which increases the emissivity of the coating and dissipates the heat through the atmosphere into space, thereby cooling down.

[0003] The design of radiation cooling materials can be divided into multilayer optical metamaterials, random dispersed particles, porous polymers, etc. In the design of radiation cooling coatings, the random dispersed particle method is the most commonly used method. By dispersing particles with high refractive index and wide optical band gap width into the coating, the coating can obtain a strong solar reflectivity and atmospheric window emissivity. For water-based radiation cooling coatings, the commonly used method is to add a large amount of inorganic particles. Although this improves the radiation cooling performance of the coating, it will cause the coating to have an ultra-high pigment volume concentration (PVC), resulting in a decrease in the overall performance of the coating. In addition, when the solar power is high, it is also necessary to consider the impact of the heat conduction effect caused by the ultra-high content of inorganic particles on the internal temperature of the building. At the same time, traditional water-based coating systems usually use styrene-acrylic and pure acrylic emulsions as film-forming materials, which inevitably cause the absorption of solar light bands and cause the coating temperature to rise.

[0004] Therefore, developing a water-based modified resin with radiation capability is an important development direction for radiant cooling coatings. Summary of the invention

[0005] Based on this, it is necessary to provide a water-based modified resin and a preparation method thereof, and a water-based radiant cooling coating to address the above problems; the water-based modified resin described in the present invention not only has obvious radiant cooling effect, but also has strong adaptability, and can be widely used in radiant cooling products such as water-based radiant cooling coatings.

[0006] A method for preparing a water-based modified resin for radiation cooling comprises the following steps:

[0007] Adding the mixture of acrylic monomer and initiator into propylene glycol methyl ether in batches for a first reaction to obtain a hydroxy acrylic acid prepolymer;

[0008] Hydroxyl-terminated polydimethylsiloxane and isophorone diisocyanate are sequentially added to the hydroxy acrylic prepolymer for a second reaction, and after the reaction is completed, the water-based modified resin is obtained by neutralization.

[0009] In one embodiment, the mass ratio of the acrylic monomer to the propylene glycol methyl ether and the initiator is (7.5-58):(5-15):(1-5).

[0010] In one embodiment, the acrylic monomer is selected from at least one of methyl methacrylate, hydroxyethyl acrylate, butyl acrylate, and methacrylic acid;

[0011] And / or, the initiator is selected from tert-butyl perbenzoate.

[0012] In one embodiment, the batch addition method is selected from dropwise addition, and the dropwise addition time is 2h-4h;

[0013] And / or, the temperature of the first reaction is 100° C.-130° C., and the time is 1 h-2 h.

[0014] In one embodiment, the mass ratio of the acrylic monomer to the isophorone diisocyanate and the hydroxyl-terminated polydimethylsiloxane is (7.5-58):(3-10):(5-15).

[0015] In one embodiment, the temperature of the second reaction is 70°C-80°C, and the time is 1h-2h.

[0016] A water-based modified resin prepared by the preparation method as described above.

[0017] A water-based radiation cooling paint comprises the water-based modified resin as described above.

[0018] In one embodiment, the water-based radiation cooling coating includes 15wt%-25wt% of water-based modified resin, 20wt%-40wt% of filler, 2wt%-8wt% of additive, 2wt%-10wt% of water-based solvent and the balance of water.

[0019] In one embodiment, the filler is selected from at least one of alumina, barium sulfate, calcium carbonate, hollow glass microspheres, hexagonal boron nitride, and aerogel;

[0020] And / or, the auxiliary agent is selected from at least one of a thickener, a film-forming auxiliary agent, a defoaming agent, and a dispersant;

[0021] And / or, the aqueous solvent is at least one selected from dipropylene glycol butyl ether, propylene glycol methyl ether, and ethylene glycol.

[0022] The invention adopts a unique preparation method, and combines hydroxyl-terminated polydimethylsiloxane with a polyurethane segment by chemical modification to form a polysiloxane flexible segment, and makes -Si-O-Si- bonds more evenly distributed in the molecular chain. On the one hand, it is not only beneficial to reduce the energy absorption of the solar light band, but also the -Si-O-Si- bonds have a good radiation cooling effect at the atmospheric window, thereby significantly enhancing the overall radiation cooling performance of the water-based radiation cooling coating with the water-based modified resin as the base material; on the other hand, the prepared water-based modified resin is more stable when used in a water dispersion, and is not prone to phase separation during the film-forming process, thereby improving the comprehensive performance of the water-based radiation cooling coating with the water-based modified resin as the base material.

[0023] Therefore, the water-based modified resin prepared in the present invention is used in a water-based radiation cooling coating, and an excellent radiation cooling effect can be achieved without increasing the amount of filler, and has a lower thermal conductivity, which can avoid the poor cooling effect of the coating caused by the excessively high thermal conductivity of the radiation material when the solar power is strong. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 The radiation temperature difference test curve diagram of Example 1, Example 2, Example 3 and Example 4 as the ambient temperature changes;

[0026] Figure 2 The radiation temperature difference test curves of Example 1, Comparative Example 1 and Comparative Example 2 as the ambient temperature changes. DETAILED DESCRIPTION

[0027] For ease of understanding of the present invention, the present invention will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. On the contrary, the purpose of providing these embodiments or examples is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the technical field of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific implementation methods or embodiments, and are not intended to limit the present invention. The optional scope of the term "and / or" used herein includes any one of two or more related listed items, and also includes any and all combinations of related listed items, and the combinations of any and all include any two related listed items, any more related listed items, or all related listed items.

[0029] In the present invention, when it comes to numerical ranges, unless otherwise specified, the above numerical ranges are deemed to be continuous and include the minimum and maximum values ​​of the range, as well as each value between such minimum and maximum values. Further, when a range refers to an integer, each integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges included therein.

[0030] The present invention provides a method for preparing a water-based modified resin for radiation cooling, comprising the following steps:

[0031] S1, adding a mixture of acrylic monomers and initiators to propylene glycol methyl ether in batches for a first reaction to obtain a hydroxy acrylic acid prepolymer;

[0032] S2, respectively adding hydroxyl-terminated polydimethylsiloxane and isophorone diisocyanate to the hydroxy acrylic prepolymer in sequence for a second reaction, and after the reaction is completed, neutralizing to obtain a water-based modified resin.

[0033] In step S1, the mass ratio of the acrylic monomer to the propylene glycol methyl ether and the initiator is (7.5-58):(5-15):(1-5), including but not limited to any point value among 7.5:5:1, 15:5:1, 22:7:1, 25:7:2, 35:10:3, 40:12:3, 45:12:4, 50:15:4, 55:15:5, and 58:15:5, or a range value between any two of them, preferably (15:5:1):(35:10:3):(50:15:4).

[0034] In one embodiment of the present invention, the acrylic monomer is selected from at least one of methyl methacrylate, hydroxyethyl acrylate, butyl acrylate and methacrylic acid, preferably a mixed monomer of methyl methacrylate, hydroxyethyl acrylate and methacrylic acid, or a mixed monomer of methyl methacrylate, hydroxyethyl acrylate, butyl acrylate and methacrylic acid.

[0035] It should be noted that the present invention does not limit the initiator used in step S1, and a conventional initiator in the art can be used. Specifically, the initiator is preferably an organic peroxide, and more preferably tert-butyl perbenzoate.

[0036] In one embodiment of the present invention, the batchwise addition method is selected from dripping, and the dripping time is 2h-4h, including but not limited to any point value of 2h, 3h, 4h or any range value between the two. It can be understood that when the same amount of mixed liquid is used, the shorter the dripping time is, the faster the dripping speed is, that is, more dripping amount is added per unit time.

[0037] In one embodiment of the present invention, the temperature of the first reaction is 100°C-130°C, including but not limited to any point value among 100°C, 110°C, 120°C, 130°C or any range value between two thereof; the time is 1h-2h, including but not limited to any point value among 1h, 1.5h, 2h or any range value between two thereof.

[0038] It is understandable that the present invention does not limit the specific process of the first reaction, and a conventional process can be used. For example, propylene glycol methyl ether is first heated to 100°C-130°C under a stirring speed of 100r / min-500r / min, and then a mixed solution of acrylic monomer and initiator is added in batches. After the batch addition is completed, the mixture is kept warm for reaction for 1h-2h, and finally the temperature is reduced to 60°C-90°C to obtain a hydroxylated acrylic acid prepolymer, and then the next step is performed.

[0039] In step S2, a unique preparation method is adopted to combine hydroxyl-terminated polydimethylsiloxane with a polyurethane segment by chemical modification to form a polysiloxane flexible segment, and the -Si-O-Si- bonds are more evenly distributed in the molecular chain. On the one hand, it is not only beneficial to reduce the energy absorption of the solar light band, but also the -Si-O-Si- bonds have a good radiation cooling effect at the atmospheric window, thereby significantly enhancing the overall radiation cooling performance of the water-based radiation cooling coating with the water-based modified resin as the base material; on the other hand, the prepared water-based modified resin is more stable when used in a water dispersion, and is not prone to phase separation during the film forming process, thereby improving the comprehensive performance of the water-based radiation cooling coating with the water-based modified resin as the base material.

[0040] It should be noted that, when adding isophorone diisocyanate and hydroxyl-terminated polydimethylsiloxane, some organic solvents, such as xylene, etc., may also be added.

[0041] In one embodiment of the present invention, the mass ratio of the acrylic monomer to the isophorone diisocyanate and the hydroxyl-terminated polydimethylsiloxane is (7.5-58):(3-10):(5-15), including but not limited to any point value among 7.5:3:5, 15:3:5, 22:5:7, 25:5:7, 30:6:7, 35:6:10, 40:8:10, 45:8:12, 50:10:12, 55:10:15, and 58:10:15, or a range value between any two of them, preferably (15:3:5):(35:6:10):(45:8:12).

[0042] In one embodiment of the present invention, the temperature of the second reaction is 70°C-80°C, including but not limited to any point value among 70°C, 75°C, 80°C or any range value between the two; the time is 1h-2h, including but not limited to any point value among 1h, 1.5h, 2h or any range value between the two.

[0043] It should be noted that after the second reaction, the isocyanate (-NCO) value in the reaction product was monitored using a standard dibutylamine back titration method. When the -NCO value was constant, the temperature was lowered to 25°C-35°C, triethylamine was added for neutralization, and deionized water was added for dispersion.

[0044] The present invention provides a water-based modified resin prepared by the preparation method as described above.

[0045] The water-based modified resin provided by the present invention is used as the base material of the water-based radiation cooling paint, which not only overcomes the problem of temperature rise of the film-forming material in the traditional water-based paint system due to absorption of sunlight, but also has cheap raw materials, good dispersibility and strong storage stability.

[0046] The present invention also provides a water-based radiation cooling paint, comprising the water-based modified resin as described above.

[0047] The water-based modified resin prepared in the present invention is used in a water-based radiation cooling coating, and an excellent radiation cooling effect can be achieved without increasing the amount of filler, and has a lower thermal conductivity, which can avoid the poor cooling effect of the coating caused by the excessively high thermal conductivity of the radiation material when the solar power is strong.

[0048] In one embodiment of the present invention, the water-based radiation cooling coating comprises 15wt%-25wt% of a water-based modified resin, 20wt%-40wt% of a filler, 2wt%-8wt% of an auxiliary agent, 2wt%-10wt% of an aqueous solvent and the remainder of water. By compounding the water-based modified resin and the filler provided by the present invention into a coating, the synergistic effect of the film-forming substance and the functional filler is utilized, so that the coating does not need to achieve a good radiation cooling effect under a higher PVC, and at the same time the coating has good dispersibility and storage properties, so that the coating has excellent comprehensive performance.

[0049] In one embodiment of the present invention, the filler is selected from at least one of aluminum oxide, barium sulfate, calcium carbonate, hollow glass microspheres, hexagonal boron nitride, and aerogel.

[0050] Preferably, the aluminum oxide is selected from nano aluminum oxide with a particle size of 500nm-1500nm; the barium sulfate is selected from nano barium sulfate with a particle size of 300nm-1000nm; the calcium carbonate is selected from nano calcium carbonate with a particle size of 300nm-700nm; the hollow glass microspheres are selected from micron-sized hollow glass microspheres with a particle size of 30μm-150μm.

[0051] More preferably, the mass ratio of the nano-alumina, the nano-calcium carbonate, the nano-barium sulfate and the micrometer-sized hollow glass microspheres is (5-10):(7-9):(5-10):(1-8).

[0052] By rationally selecting nanofillers and optimizing the dosage of fillers, on the one hand, by compounding materials with high reflectivity of ultraviolet light, visible light, and near-infrared light, the coating formed by the paint can obtain high reflectivity in the overall solar band and high atmospheric window emissivity, thereby making the coating have a stronger radiation cooling effect; on the other hand, by using low thermal conductivity fillers, the coating formed by the paint can have both excellent radiation cooling effect and lower thermal conductivity.

[0053] In one embodiment of the present invention, the auxiliary agent is selected from at least one of a thickener, a film-forming auxiliary agent, a defoaming agent, and a dispersant.

[0054] Specifically, the thickener includes but is not limited to at least one of cellulose ether and its derivatives, polyurethane and inorganic thickeners; the film-forming aid includes but is not limited to at least one of 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, diisobutyl succinate and dipropylene glycol butyl ether; the defoamer includes but is not limited to at least one of silicone defoamers and mineral oil defoamers; the dispersant includes but is not limited to at least one of polycarboxylate dispersants and polyether dispersants.

[0055] In one embodiment of the present invention, the aqueous solvent is selected from at least one of dipropylene glycol butyl ether, propylene glycol methyl ether and ethylene glycol.

[0056] It should be noted that the present invention does not limit the preparation method of the water-based radiation cooling coating, and it can be prepared by a conventional method, for example: under the stirring speed condition of 500r / min-800r / min, first add part of deionized water, part of thickener, aqueous solvent, part of dispersant, part of film-forming aid, and part of defoamer to the dispersion tank, disperse for 0.5h-1h, disperse evenly, and obtain a first mixed solution; under the stirring speed condition of 500r / min-800r / min, add filler to the first mixed solution, adjust the speed to 1800r / min-2500r / min, and stir until the mixture is uniform. in, high-speed dispersion for 2h-3h to obtain a second mixed liquid; adjust the speed to 200r / min-500r / min, add part of the defoamer, the substrate wetting agent, and the remaining thickener to the second mixed liquid, and continue to disperse for 0.5h-1h. After the dispersion is completed, an aqueous radiation cooling slurry is obtained; under the stirring speed condition of 500r / min-800r / min, the remaining deionized water, the remaining dispersant, the remaining film-forming aid, the remaining defoamer, the aqueous radiation cooling slurry, and the aqueous modified resin dispersion are added to the dispersion tank in sequence, and dispersed for 0.5h-1h to obtain an aqueous radiation cooling coating.

[0057] It is understandable that the water-based radiant cooling paint described in the present invention can be used in outdoor scenes such as building facades, and the present invention does not limit this.

[0058] Hereinafter, the water-based modified resin and its preparation method and water-based radiant cooling coating will be further described by the following specific examples. However, those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. If no specific conditions are specified in the examples, the conventional conditions or the conditions recommended by the manufacturer are followed. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be obtained commercially.

[0059] Example 1

[0060] (1) Preparation of water-based modified resin:

[0061] 7 parts by mass of propylene glycol methyl ether were added into a four-necked flask equipped with a stirring blade, a thermometer, a constant pressure dropping funnel, and a condenser. The temperature was raised to 120° C. at a speed of 500 r / min. A mixed solution consisting of 10 parts by mass of methyl methacrylate, 8 parts by mass of hydroxyethyl acrylate, 4 parts by mass of methacrylic acid, and 1 part by mass of tert-butyl perbenzoate was added into the constant pressure dropping funnel and uniformly added dropwise into the four-necked flask. The addition time was 3 hours. After the addition was completed, the mixture was kept warm for 2 hours to obtain a hydroxy acrylic acid prepolymer.

[0062] The temperature was lowered to 80°C, 15 parts by mass of dihydroxy-terminated polydimethylsiloxane was added to a constant pressure dropping funnel, and the mixture was uniformly added to a four-necked flask for 0.5 h. After the addition was completed, the mixture was dispersed for 0.5 h. 7 parts by mass of isophorone diisocyanate and 1.5 parts by mass of a xylene mixture were added to a constant pressure dropping funnel, and the mixture was uniformly added to a four-necked flask for 1 h. The mixture was kept warm for reaction for 1 h. The temperature was lowered to 35°C, 4 parts by mass of triethylamine was added, and the mixture was neutralized for 0.5 h to obtain a water-based modified resin.

[0063] (2) Preparation of water-based radiation cooling coating:

[0064] At a speed of 500 r / min, 50 parts by mass of deionized water, 0.3 parts by mass of thickener (HBR 250), 11 parts by mass of aqueous solvent (dipropylene glycol butyl ether), 2 parts by mass of dispersant (SN 5040), 1.2 parts by mass of film-forming aid (ethylene glycol), and 2 parts by mass of defoamer (A 220) were dispersed for 0.5 h and uniformly dispersed to obtain a first mixed solution; 10 parts by mass of nano barium sulfate (particle size 500 nm), 9 parts by mass of nano alumina (particle size 500 nm), 10 parts by mass of nano calcium carbonate (particle size 1 μm), and 5 parts by mass of hollow glass microspheres (particle size 30 μm) were added to the first mixed solution, the speed was adjusted to 2000 r / min, and high-speed dispersion was performed for 2 h to obtain a second mixed solution; the speed was adjusted to 500 r / min, 1 part by mass of substrate wetting agent, 0.5 parts by mass of thickener (R 2020), continue to disperse for 0.5-1h, and after dispersion is completed, obtain an aqueous radiation cooling slurry;

[0065] At a speed of 500r / min, 17 parts by mass of ionized water, 1 part by mass of dispersant (BYK 194N), 1 part by mass of film-forming aid (TEX), 1 part by mass of defoamer (A 220), 57 parts by mass of aqueous radiation cooling slurry, and 23 parts by mass of aqueous modified resin were added to a dispersion tank in sequence and dispersed for 1 hour to obtain a water-based radiation cooling coating.

[0066] Example 2

[0067] The difference between Example 2 and Example 1 is that 10 parts by mass of titanium dioxide and 14 parts by mass of barium sulfate (particle size 2 μm) are used instead of 9 parts by mass of nano-alumina (particle size 500 nm), 10 parts by mass of nano-calcium carbonate (particle size 1 μm), and 5 parts by mass of hollow glass microspheres (particle size 30 μm).

[0068] Example 3

[0069] (1) Preparation of water-based modified resin:

[0070] 9 parts by mass of propylene glycol methyl ether were added into a four-necked flask equipped with a stirring blade, a thermometer, a constant pressure dropping funnel, and a condenser. The temperature was raised to 120° C. at a speed of 300 r / min. A mixed solution consisting of 6 parts by mass of methyl methacrylate, 9 parts by mass of hydroxyethyl acrylate, 3 parts by mass of butyl acrylate, 4 parts by mass of methacrylic acid, and 2 parts by mass of tert-butyl perbenzoate was added into the constant pressure dropping funnel and uniformly added dropwise into the four-necked flask for 2 hours. After the addition was completed, the mixture was kept warm for 2 hours to obtain a hydroxy acrylic acid prepolymer.

[0071] The temperature was lowered to 70°C, 5 parts by mass of dihydroxy-terminated polydimethylsiloxane were added to a constant pressure dropping funnel, and the mixture was uniformly added to a four-necked flask for 0.5 h. After the addition was completed, the mixture was dispersed for 0.5 h. 10 parts by mass of isophorone diisocyanate and 2 parts by mass of a mixed solution of xylene were added to a constant pressure dropping funnel, and the mixture was uniformly added to a four-necked flask for 1 h. The mixture was kept warm for reaction for 1 h. The temperature was lowered to 35°C, 4 parts by mass of triethylamine were added, and the mixture was neutralized for 0.5 h to obtain a water-based modified resin.

[0072] (2) Preparation of water-based radiation cooling coating:

[0073] At a speed of 500 r / min, 50 parts by mass of deionized water, 0.3 parts by mass of thickener (HBR 250), 11 parts by mass of aqueous solvent (dipropylene glycol butyl ether), 2 parts by mass of dispersant (SN 5040), 1.2 parts by mass of film-forming aid (ethylene glycol), and 2 parts by mass of defoamer (A 220) were dispersed for 0.5 h and uniformly dispersed to obtain a first mixed solution; 10 parts by mass of nano barium sulfate (particle size 500 nm), 10 parts by mass of nano alumina (particle size 500 nm), 10 parts by mass of nano calcium carbonate (particle size 1 μm), and 5 parts by mass of hollow glass microspheres (particle size 30 μm) were added to the first mixed solution, the speed was adjusted to 2000 r / min, and high-speed dispersion was performed for 2 h to obtain a second mixed solution; the speed was adjusted to 500 r / min, and 1 part by mass of substrate wetting agent, 0.5 parts by mass of thickener (R 2020), continue to disperse for 0.5-1h, and after dispersion is completed, obtain an aqueous radiation cooling slurry;

[0074] At a speed of 500r / min, 15 parts by mass of ionized water, 1 part by mass of dispersant (BYK 194N), 1 part by mass of film-forming aid (TEX), 1 part by mass of defoamer (A 220), 55 parts by mass of aqueous radiation cooling slurry, and 25 parts by mass of aqueous modified resin were added to a dispersion tank in sequence and dispersed for 1 hour to obtain a water-based radiation cooling coating.

[0075] Example 4

[0076] (1) Preparation of water-based modified resin:

[0077] 10 parts by mass of propylene glycol methyl ether were added into a four-necked flask equipped with a stirring blade, a thermometer, a constant pressure dropping funnel, and a condenser. The temperature was raised to 120° C. at a speed of 500 r / min. A mixed solution consisting of 12 parts by mass of methyl methacrylate, 8 parts by mass of hydroxyethyl acrylate, 6 parts by mass of methacrylic acid, and 3 parts by mass of tert-butyl perbenzoate was added into the constant pressure dropping funnel and uniformly added dropwise into the four-necked flask. The addition time was 3 hours. After the addition was completed, the mixture was kept warm for 1 hour to obtain a hydroxy acrylic acid prepolymer.

[0078] The temperature was lowered to 80°C, 15 parts by mass of dihydroxy-terminated polydimethylsiloxane was added to a constant pressure dropping funnel, and the mixture was uniformly added to a four-necked flask for 0.5 h. After the addition was completed, the mixture was dispersed for 0.5 h. 3 parts by mass of isophorone diisocyanate and 1 part by mass of a xylene mixture were added to a constant pressure dropping funnel, and the mixture was uniformly added to a four-necked flask for 1 h. The mixture was kept warm for reaction for 1 h. The temperature was lowered to 35°C, 4 parts by mass of triethylamine were added, and the mixture was neutralized for 0.5 h to obtain a water-based modified resin.

[0079] (2) Preparation of water-based radiation cooling coating:

[0080] At a speed of 500 r / min, 50 parts by mass of deionized water, 0.3 parts by mass of thickener (HBR 250), 11 parts by mass of aqueous solvent (dipropylene glycol butyl ether), 2 parts by mass of dispersant (SN 5040), 1.2 parts by mass of film-forming aid (ethylene glycol), and 2 parts by mass of defoamer (A 220) were dispersed for 0.5 h and uniformly dispersed to obtain a first mixed solution; 20 parts by mass of nano barium sulfate (particle size 500 nm), 10 parts by mass of nano calcium carbonate (particle size 1 μm), and 5 parts by mass of hollow glass microspheres (particle size 30 μm) were added to the first mixed solution, the speed was adjusted to 2000 r / min, and high-speed dispersion was performed for 2 h to obtain a second mixed solution; the speed was adjusted to 500 r / min, and 1 part by mass of substrate wetting agent, 0.5 parts by mass of thickener (R 2020), continue to disperse for 0.5-1h, and after dispersion is completed, obtain an aqueous radiation cooling slurry;

[0081] At a speed of 500r / min, 10 parts by mass of ionized water, 1 part by mass of dispersant (BYK 194N), 1 part by mass of film-forming aid (TEX), 1 part by mass of defoamer (A 220), 50 parts by mass of aqueous radiation cooling slurry, and 30 parts by mass of aqueous modified resin were added to a dispersion tank in sequence and dispersed for 1 hour to obtain a water-based radiation cooling coating.

[0082] Comparative Example 1

[0083] The difference between Comparative Example 1 and Example 1 is that 15 parts by mass of trimethylolpropane is used instead of 15 parts by mass of bishydroxy-terminated polydimethylsiloxane.

[0084] Comparative Example 2

[0085] The difference between Comparative Example 2 and Example 1 is that 7 parts by mass of toluene diisocyanate are used instead of 7 parts by mass of isophorone diisocyanate.

[0086] Comparative Example 3

[0087] The difference between Comparative Example 3 and Example 1 is that 15 parts by mass of dihydroxy-terminated polydimethylsiloxane, 7 parts by mass of isophorone diisocyanate, and 1.5 parts by mass of xylene are added into a constant pressure dropping funnel, and then added dropwise into the four-necked flask at a uniform speed.

[0088] The coatings prepared in the above examples and comparative examples were formed into coatings of the same thickness and area, and the radiation cooling performance of the coatings was tested using a temperature measuring device for testing the radiation cooling temperature difference, which consisted of a self-made temperature measuring box, a data recorder, a computer, and a solar radiation meter. The test results are as follows: Figure 1 and Figure 2 shown.

[0089] according to Figure 1 and Figure 2 It can be seen that the coatings formed by the coatings prepared in Examples 1-3 can be lower than the ambient temperature for most of the test period, and have an obvious radiation cooling effect. In Example 4, due to the addition of a small amount of titanium dioxide as a filler, the coating produces a certain light absorption effect in the ultraviolet light band, resulting in an increase in the coating temperature compared with Example 1; compared with Example 2, it can be seen that in Example 1, the radiation cooling effect is better through the reasonable selection and dosage optimization of nanofillers; while in Comparative Example 1, the radiation cooling effect is poor because no -Si-O-Si- bond is formed; in Comparative Example 2, due to the strong reaction activity of toluene diisocyanate with hydroxyl groups, the resin molecular weight is difficult to control, the resin viscosity is large, and the dispersion with the powder is uneven during the preparation of the coating, which reduces the radiation effect of the coating; in Comparative Example 3, due to the strong reaction activity of the co-mixing of dihydroxy-terminated polydimethylsiloxane and isophorone diisocyanate, the water-based modified resin was not successfully prepared.

[0090] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0091] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing a water-based modified resin for radiation cooling, characterized in that: The preparation method comprises the following steps: Adding a mixture of acrylic acid monomers and initiators into propylene glycol methyl ether in batches for a first reaction to obtain a hydroxy acrylic acid prepolymer; Hydroxyl-terminated polydimethylsiloxane and isophorone diisocyanate are sequentially added to the hydroxy acrylic prepolymer for a second reaction, and after the reaction is completed, the water-based modified resin is obtained by neutralization.

2. The method for preparing the water-based modified resin according to claim 1, characterized in that: The mass ratio of the acrylic monomer to the propylene glycol methyl ether and the initiator is (7.5-58):(5-15):(1-5).

3. The method for preparing the water-based modified resin according to claim 1 or 2, characterized in that: The acrylic monomer is selected from at least one of methyl methacrylate, hydroxyethyl acrylate, butyl acrylate and methacrylic acid; And / or, the initiator is selected from tert-butyl perbenzoate.

4. The method for preparing the water-based modified resin according to claim 1, characterized in that: The batch addition method is selected from dropwise addition, and the dropwise addition time is 2h-4h; And / or, the temperature of the first reaction is 100° C.-130° C., and the time is 1 h-2 h.

5. The method for preparing the water-based modified resin according to claim 1, characterized in that: The mass ratio of the acrylic monomer to the isophorone diisocyanate and the hydroxyl-terminated polydimethylsiloxane is (7.5-58):(3-10):(5-15).

6. The method for preparing a water-based modified resin according to claim 1, characterized in that: The temperature of the second reaction is 70°C-80°C, and the time is 1h-2h.

7. A water-based modified resin obtained by the preparation method according to any one of claims 1 to 6.

8. A water-based radiation cooling paint, characterized in that: Comprising the water-based modified resin as described in claim 7.

9. The water-based radiant cooling paint according to claim 8, characterized in that: The water-based radiation cooling paint comprises 15wt%-25wt% of water-based modified resin, 20wt%-40wt% of filler, 2wt%-8wt% of auxiliary agent, 2wt%-10wt% of water-based solvent and the balance of water.

10. The water-based radiant cooling paint according to claim 9, characterized in that: The filler is selected from at least one of alumina, barium sulfate, calcium carbonate, hollow glass microspheres, hexagonal boron nitride, and aerogel; And / or, the auxiliary agent is selected from at least one of a thickener, a film-forming auxiliary agent, a defoaming agent, and a dispersant; And / or, the aqueous solvent is at least one selected from dipropylene glycol butyl ether, propylene glycol methyl ether, and ethylene glycol.

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