A reflective heat-insulating coating and its preparation method and application

Abstract

The present invention belongs to the field of coating technology, and particularly relates to a reflective heat-insulating coating, a preparation method thereof, and an application thereof. The reflective heat-insulating coating of the present invention comprises hollow acrylic emulsion A, hollow acrylic emulsion B, hollow acrylic emulsion C, and elastic acrylic emulsion; the latex particles in hollow acrylic emulsion A, hollow acrylic emulsion B, and hollow acrylic emulsion C are all hollow microspheres; the ratio of the thickness of the shell layer of the hollow microspheres to the particle size of the hollow microspheres is (9-33):100; the particle sizes of the latex particles in hollow acrylic emulsion A, hollow acrylic emulsion B, and hollow acrylic emulsion C are 450-750nm, 900-1300nm, and 1400-1800nm, respectively. The present invention adopts three hollow acrylic emulsions of different particle sizes to compound, and the hollow microspheres of different sizes have a synergistic effect, which is beneficial to improving the reflective heat-insulating performance, mechanical properties, stain resistance, and weather resistance of the coating.

Description

Technical Field

[0001] The present invention belongs to the technical field of coatings, and in particular relates to a reflective heat-insulating coating and a preparation method and application thereof. Background Art

[0002] With the development and progress of society, energy-saving urban building materials have attracted much attention. Energy-saving buildings can significantly reduce energy consumption, alleviate energy supply pressure, reduce environmental pollution, and better meet ecological needs.

[0003] Reflective insulation is a key performance metric for exterior architectural coatings, but existing exterior coatings offer limited reflective insulation. Some studies have attempted to improve reflective insulation by adding glass microspheres, but these have poor tensile strength and are prone to cracking over time, damaging the paint film. Other studies have attempted to improve reflective insulation by adding polyethylene hollow microspheres, but these exhibit poor weather resistance and, as exterior coatings, can yellow and age, and their reflective insulation performance needs further improvement. In short, current reflective insulation coatings struggle to balance reflective insulation, mechanical properties, and weather resistance.

[0004] Therefore, it is of great significance to provide a coating that has good reflective thermal insulation performance, mechanical properties and weather resistance. Summary of the Invention

[0005] The present invention aims to address one or more of the above-mentioned technical problems in the prior art, and at least provide a beneficial alternative or create a favorable condition. Specifically, the present invention provides a reflective and heat-insulating coating with excellent reflective and heat-insulating properties, mechanical properties, and weather resistance, which can meet the coating performance requirements of exterior wall buildings.

[0006] The inventive concept of the present invention is as follows: the coating of the present invention comprises a hollow acrylic emulsion A, a hollow acrylic emulsion B, a hollow acrylic emulsion C, and an elastic acrylic emulsion; the particle sizes of the latex particles in the hollow acrylic emulsion A, the hollow acrylic emulsion B, and the hollow acrylic emulsion C are 450-750 nm, 900-1300 nm, and 1400-1800 nm, respectively; the latex particles in the hollow acrylic emulsion A, the hollow acrylic emulsion B, and the hollow acrylic emulsion C are all hollow microspheres; the hollow microspheres include a shell layer, and the ratio of the thickness of the shell layer to the particle size of the hollow microspheres is (9-33):100. The hollow polymer microspheres of the present invention are filled with water in a liquid state, and after the water evaporates and dries, the cavity is filled with air. Due to the large difference in refractive index between the shell polymer and the air in the hollow part, the coating can be given good thermal insulation and light-shielding properties. In addition, the polymer hollow microspheres have excellent properties such as deformability and low specific gravity, which make the coating have better tensile strength and can better resist cracking of the base layer. At the same time, the present invention uses three hollow acrylic emulsions with different particle size ranges to compound. The hollow microspheres of different sizes can play a synergistic role. The shell layer of the hollow microspheres and the particle size of the hollow microspheres have a specific size relationship, which is conducive to improving the reflective thermal insulation performance, mechanical properties, stain resistance and weather resistance of the coating.

[0007] Therefore, a first aspect of the present invention provides a reflective, thermally insulating coating.

[0008] Specifically, the reflective heat-insulating coating includes hollow acrylic emulsion A, hollow acrylic emulsion B, hollow acrylic emulsion C, and elastic acrylic emulsion;

[0009] The particle sizes of the latex particles in the hollow acrylic emulsion A, the hollow acrylic emulsion B, and the hollow acrylic emulsion C are 450-750 nm, 900-1300 nm, and 1400-1800 nm, respectively;

[0010] The latex particles in the hollow acrylic emulsion A, the hollow acrylic emulsion B, and the hollow acrylic emulsion C are all hollow microspheres; the hollow microspheres include a shell layer, and the ratio of the thickness of the shell layer to the particle size of the hollow microspheres is (9-33):100.

[0011] Preferably, the hollow microspheres include a shell layer; the ratio of the thickness of the shell layer to the particle size of the hollow microspheres is (10-30):100.

[0012] Preferably, the particle sizes of the latex particles in the hollow acrylic emulsion A, the hollow acrylic emulsion B, and the hollow acrylic emulsion C are 500-700 nm, 1000-1200 nm, and 1500-1700 nm, respectively.

[0013] Preferably, in the coating, the hollow acrylic emulsion A, the hollow acrylic emulsion B, and the hollow acrylic emulsion C are all 1.8-11 parts by weight.

[0014] More preferably, in the coating, the hollow acrylic emulsion A, the hollow acrylic emulsion B, and the hollow acrylic emulsion C are all 2-10 parts by weight.

[0015] Preferably, the solid content of the elastic acrylic emulsion is 45-60%; further preferably, the solid content of the elastic acrylic emulsion is 48-55%.

[0016] Preferably, the particle size of the latex particles in the elastic acrylic emulsion is 90-330 nm; further preferably, the particle size of the latex particles in the elastic acrylic emulsion is 100-300 nm.

[0017] Preferably, the coating further comprises at least one of a filler, a wetting agent, a dispersant, a defoaming agent, a thickener, a bactericide, a preservative, a mildew preventer, a pH regulator, an antifreeze-thaw aid, a film-forming aid, a functional aid, and water.

[0018] Preferably, the coating comprises hollow acrylic emulsion A, hollow acrylic emulsion B, hollow acrylic emulsion C, elastic acrylic emulsion, filler, wetting agent, dispersant, defoamer, thickener, bactericide, preservative, mildewproof agent, pH regulator, antifreeze-thaw aid, film-forming aid, functional additive, and water; and in parts by weight, the coating comprises hollow acrylic emulsion A 1.8-11 parts, hollow acrylic emulsion B 1.8-11 parts, hollow acrylic emulsion C 1.8-11 parts, elastic acrylic emulsion 18-33 parts, filler 23-40 parts, wetting agent 0.27-0.55 parts, dispersant 0.55-1.2 parts, defoaming agent 0.55-1.1 parts, thickener 0.27-0.55 parts, bactericide 0.1-0.33 parts, preservative 0.18-0.33 parts, mildewproof agent 0.18-0.44 parts, pH adjuster 0.1-0.22 parts, antifreeze-thaw aid 0.9-2.2 parts, film-forming aid 0.45-1.1 parts, functional additive 0.9-2.2 parts, water 20-25 parts.

[0019] Further preferably, the coating comprises hollow acrylic emulsion A, hollow acrylic emulsion B, hollow acrylic emulsion C, elastic acrylic emulsion, filler, wetting agent, dispersant, defoamer, thickener, bactericide, preservative, mildewproof agent, pH regulator, antifreeze-thaw aid, film-forming aid, functional additive, and water; and in parts by weight, the coating comprises 2-10 parts of hollow acrylic emulsion A, 2-10 parts of hollow acrylic emulsion B, 10 parts of hollow acrylic emulsion C, 10 parts of hollow acrylic emulsion B, 10 parts of hollow acrylic emulsion C, 10 parts of hollow acrylic emulsion A ... 2-10 parts, elastic acrylic emulsion 20-30 parts, filler 25-38 parts, wetting agent 0.3-0.5 parts, dispersant 0.6-1.1 parts, defoaming agent 0.6-1.0 parts, thickener 0.3-0.5 parts, bactericide 0.1-0.3 parts, preservative 0.2-0.3 parts, mildew inhibitor 0.2-0.4 parts, pH regulator 0.1-0.2 parts, antifreeze-thaw aid 1-2 parts, film-forming aid 0.5-1.0 parts, functional additive 1-2 parts, water 20-25 parts.

[0020] Preferably, the filler includes at least one of calcite powder, titanium dioxide and diatomaceous earth; further preferably, the filler includes calcite powder, titanium dioxide and diatomaceous earth.

[0021] Preferably, the wetting agent includes at least one of anionic wetting agents and nonionic wetting agents.

[0022] Preferably, the dispersant comprises at least one of polycarboxylates, polyacrylates, and carboxylic acid copolymer salts.

[0023] Preferably, the defoaming agent includes at least one of polymer composite mineral oil, metal soap defoaming agent, and silicone defoaming agent.

[0024] Preferably, the thickener comprises hydroxyethyl cellulose.

[0025] Preferably, the fungicide includes at least one of pyrimidine copper zinc thiocarbamate and zinc oxide; further preferably, the fungicide includes pyrimidine copper zinc thiocarbamate and zinc oxide.

[0026] Preferably, the preservative includes at least one of 5-chloro-2-methyl-4-isothiazoline-3-one and 2-methyl-4-isothiazoline-3-one; further preferably, the preservative includes 5-chloro-2-methyl-4-isothiazoline-3-one and 2-methyl-4-isothiazoline-3-one.

[0027] Preferably, the mildewcide comprises methyl 2-benzimidazolecarbamate.

[0028] Preferably, the pH adjuster comprises 2-amino-2-methyl-1-propanol.

[0029] Preferably, the antifreeze-thaw aid comprises propylene glycol.

[0030] Preferably, the film-forming aid comprises lauryl alcohol ester.

[0031] Preferably, the functional auxiliary agent includes a non-ionic polyurethane leveling modifier.

[0032] Preferably, the raw materials for preparing the hollow acrylic emulsion A, the hollow acrylic emulsion B, and the hollow acrylic emulsion C all include an emulsifier, an unsaturated acid, an olefin monomer, an initiator, a seed emulsion, and water;

[0033] The raw materials for preparing the seed emulsion include an emulsifier, an unsaturated acid, an olefin monomer, an initiator, a silicone compound with an active group, and water.

[0034] Preferably, the emulsifier is selected from at least one of sodium dodecylbenzene sulfonate, sodium lauryl sulfate, fatty alcohol polyoxyethylene ether, polyoxyethylene alkyl ester, and sodium cetyl betaine.

[0035] Preferably, the unsaturated acid is selected from at least one of acrylic acid, methacrylic acid, itaconic acid and fumaric acid.

[0036] Preferably, the olefin monomer is selected from at least one of styrene, methyl methacrylate, butyl acrylate, acrylonitrile and isooctyl acrylate.

[0037] Preferably, the initiator is selected from at least one of sodium persulfate, ammonium persulfate and potassium persulfate.

[0038] Preferably, the siloxane compound with active groups is prepared by a preparation method comprising the following steps: methacryloxypropyl alkoxysilane reacts with alkyl silicate to prepare the siloxane compound with active groups.

[0039] Specifically, the siloxane compound with active groups can improve the stability of hollow microspheres during the synthesis process, solve the problem that hollow microspheres are easily broken during expansion, improve the thermal insulation performance of hollow acrylic emulsion, and thus make the coating prepared using the siloxane compound have good reflective thermal insulation effect.

[0040] The second aspect of the present invention provides a method for preparing the reflective heat-insulating coating according to the first aspect of the present invention.

[0041] Specifically, the preparation method of the reflective heat-insulating coating comprises the following steps:

[0042] The coating is prepared by mixing various raw material components.

[0043] Preferably, the method for preparing the reflective heat-insulating coating comprises the following steps:

[0044] (1) dissolving the dispersant and wetting agent in water, adding the thickener, and then adding the pH adjuster and filler, mixing to obtain a premix;

[0045] (2) mixing the remaining components with the premix obtained in step (1) to prepare the coating.

[0046] Preferably, in step (1), the thickener is added and mixed until the solution becomes a slurry, and then the pH adjuster and filler are added and mixed to obtain a premix.

[0047] Preferably, step (2) is specifically as follows: when the particle size of the premix obtained in step (1) is less than 50 μm, a bactericide, a preservative, a mildew inhibitor, an antifreeze-thaw aid, a film-forming aid and a functional additive are added and mixed, and then hollow acrylic emulsion A, hollow acrylic emulsion B, hollow acrylic emulsion C, elastic acrylic emulsion and a defoaming agent are added and mixed to prepare the reflective heat-insulating coating.

[0048] Preferably, the preparation methods of the hollow acrylic emulsion A, the hollow acrylic emulsion B, and the hollow acrylic emulsion C all comprise the following steps:

[0049] S1: reacting an emulsifier, an unsaturated acid, an olefin monomer, an initiator, a silicone compound with an active group, and water to prepare the seed emulsion;

[0050] S2: reacting an emulsifier, an unsaturated acid, an olefin monomer, an initiator, water and the seed emulsion obtained in step (1) to prepare the hollow acrylic emulsion A, the hollow acrylic emulsion B or the hollow acrylic emulsion C.

[0051] Preferably, step S1 specifically includes the following steps: mixing an emulsifier, an unsaturated acid, an olefin monomer and water, first adding part of the initiator to carry out reaction a, then adding the remaining initiator to carry out reaction b, and finally adding a siloxane compound with an active group to carry out reaction c to obtain the seed emulsion.

[0052] Preferably, the reaction a is carried out at 80-90° C. for 10-20 min; further preferably, the reaction a is carried out at 83-85° C. for 10-20 min.

[0053] Preferably, the reaction b is carried out at 80-90° C. for 3-5 h; further preferably, the reaction b is carried out at 83-85° C. for 3.5-4.5 h.

[0054] Preferably, the reaction c is carried out at 80-90° C. for 1-3 h; further preferably, the reaction c is carried out at 83-85° C. for 1.5-2.5 h.

[0055] Preferably, step S2 specifically includes the following steps: mixing the seed emulsion and water, adding part of the initiator, slowly adding a mixture consisting of an emulsifier, an unsaturated acid, an olefin monomer, and the remaining initiator, and reacting to obtain the hollow acrylic emulsion A, hollow acrylic emulsion B, or hollow acrylic emulsion C.

[0056] Preferably, the reaction temperature of the reaction in step S2 is 80-93°C; further more preferably, the reaction temperature of the reaction in step S2 is 85-88°C.

[0057] Preferably, in step S2, after completion of the reaction, post-treatment is performed using tert-butyl hydroperoxide and ascorbic acid.

[0058] The third aspect of the present invention provides a use of the reflective heat-insulating coating described in the first aspect of the present invention in the field of construction.

[0059] Preferably, the construction field includes building exterior walls.

[0060] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0061] (1) The present invention utilizes three hollow acrylic emulsions with different particle size ranges for compounding. Hollow microspheres of different sizes can play a synergistic role, and the shell layer of the hollow microspheres and the particle size of the hollow microspheres have a specific size relationship, which is beneficial to the reflective heat insulation performance, mechanical properties, stain resistance, and weather resistance of the coating. The reflective heat insulation coating of the present invention has a solar reflectance of 0.86-0.88, a near-infrared reflectance of 0.87-0.9, and a hemispherical emissivity of up to 0.91-0.93. The temperature in the measuring room during the thermal insulation performance test can even be reduced by 11.8°C. The tensile strength is 2.82-2.89 MPa, and the elongation at break is 488-507%. It has great application potential in the field of building walls.

[0062] (2) The latex particles in the hollow acrylic emulsion of the present invention are polymer microspheres with a hollow structure. When in a liquid state, the cavity is filled with water, and after the water evaporates and dries, the cavity is filled with air. Since the refractive index of the shell polymer and the air in the hollow part is quite different, the coating can be given good heat insulation and light-shielding properties. In addition, the polymer hollow microspheres have excellent properties such as deformability and low specific gravity, which makes the coating have better mechanical properties and can better resist cracking of the base layer.

[0063] (3) The preparation process of the present invention is simple and convenient for large-scale production and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 Schematic diagram of the device for testing thermal insulation performance of the present invention. DETAILED DESCRIPTION

[0065] In order to make the technical solution of the present invention more clearly understood by those skilled in the art, the following examples are given for illustration. It should be noted that the following examples do not limit the scope of protection claimed by the present invention.

[0066] Unless otherwise specified, the raw materials, reagents, or devices used in the following examples can be obtained from conventional commercial sources or by existing known methods.

[0067] Example 1

[0068] A reflective heat-insulating coating, comprising, by weight, 4 parts of a hollow acrylic emulsion A with a latex particle size of 450 nm, 3 parts of a hollow acrylic emulsion B with a latex particle size of 900 nm, and 3 parts of a hollow acrylic emulsion C with a latex particle size of 1700 nm. 3 parts, elastic acrylic emulsion 25 parts, filler 26 parts (calcite powder 5 parts, rutile titanium dioxide 20 parts, diatomaceous earth 1 part), nonionic alkyl polyoxyethylene ether wetting agent 0.4 parts, polyacrylate ammonium salt dispersant 0.6 parts, mineral oil defoamer 0.6 parts, thickener hydroxyethyl cellulose 0.3 parts, fungicide (a mixture of pyrimidine copper zinc and zinc oxide) 0.3 parts, preservative (a mixture of 5-chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-4-isothiazolin-3-one) 0.3 parts, mildewproof agent 2-benzimidazole methyl carbamate 0.4 parts, pH adjuster 2-amino-2-methyl-1-propanol 0.1 parts, antifreeze-thaw aid propylene glycol 2 parts, film-forming aid dodecyl alcohol ester 0.5 parts, functional additive nonionic polyurethane leveling agent 2 parts, water 25 parts;

[0069] The latex particles in hollow acrylic emulsion A, hollow acrylic emulsion B, and hollow acrylic emulsion C are all hollow microspheres;

[0070] The ratio of the shell thickness to the particle size of the three hollow microspheres is 20:100.

[0071] A method for preparing a reflective heat-insulating coating comprises the following steps:

[0072] Add water, a wetting agent, a dispersant, and 20% of a defoaming agent while stirring at 200 rpm, and stir for 3 minutes; adjust the speed to 400 rpm, add a thickener, and stir for 2 minutes; adjust the speed to 1200 rpm, add a filler, and stir for 15 minutes; adjust the speed to 900 rpm, add a film-forming agent, an antifreeze agent, and a bactericidal, mildew-proof, and preservative, and stir for 3 minutes; then add hollow acrylic emulsion A, hollow acrylic emulsion B, hollow acrylic emulsion C, and elastic acrylic emulsion, and stir for 3 minutes; add a functional additive and stir for 3 minutes; add the remaining defoaming agent, and stir evenly to prepare a reflective and heat-insulating coating.

[0073] The method for preparing a hollow acrylic emulsion with a latex particle size of 450 nm comprises the following steps:

[0074] (1) First, 100 g of ethyl silicate was added to 50 g of deionized water and stirred evenly. During the stirring process, 0.01 g of acetic acid was added, the temperature was raised to 45° C., and stirring was continued for 5 min. Then, 10 g of γ-methacryloxypropyltriethoxysilane monomer was dropped into the water. After reacting for 30 min, the temperature was lowered, and 0.1% (w / v) of tetrahydroxypropylethylenediamine was added to the mixture as a stabilizer. Finally, the mixture was filtered to obtain a siloxane compound with an active group.

[0075] (2) 1 part of the emulsifier sodium dodecylbenzenesulfonate (DS-4) was dispersed in 16.43 parts of deionized water, 21.36 parts of the olefin monomer methyl methacrylate (MMA) and 11.5 parts of the unsaturated acid methacrylic acid (MAA) were slowly added to the water under stirring, and dispersed at a speed of 600 rpm for 10 minutes to prepare a pre-emulsion for dropwise addition reaction; sodium persulfate and water were mixed evenly and used as a titration initiator;

[0076] (3) Prepare a reaction flask, add 23.66 parts of water into it, heat it to 85°C, add 20% of the pre-emulsion (a total of 50.29 parts of the pre-emulsion), and add an aqueous solution of 0.13 parts of sodium persulfate and 0.82 parts of water, maintain the reaction at 84°C for 15 minutes, and show a blue fluorescent state; continue to dropwise add the remaining pre-emulsion and the aqueous solution of 0.07 parts of sodium persulfate and 8.22 parts of water at 84°C at a uniform rate, and stir at a uniform rate for 4 hours until the reaction forms an emulsion; then add 6.67 parts of the siloxane compound with active groups obtained in step (1) into the reaction flask at one time, wash it with water, control the temperature to 84°C, keep the temperature for reaction for 2 hours, and finally cool it down, filter the emulsion, and prepare a seed emulsion;

[0077] (4) 14.59 parts of seed emulsion were added to 36.47 parts of water, and the temperature was raised to 92°C. An aqueous solution of 0.07 parts of sodium persulfate and 0.36 parts of water was added, and an emulsion consisting of 0.51 parts of sodium dodecylbenzenesulfonate (DS-4), 21.74 parts of styrene (ST), 1.46 parts of methyl methacrylate (MMA), 0.05 parts of allyl methacrylate (AMA), 0.15 parts of methacrylic acid (MAA), and 17.51 parts of water and 0. 0.7 parts of sodium persulfate and 3.65 parts of water aqueous solution, the dropwise addition time is 150 minutes, when the emulsion is added to 45%, 1.09 parts of ammonia water is added, the reaction is carried out for 5 minutes, and the dropwise addition is continued; after the dropwise reaction, the temperature is lowered to 82 ° C, and tert-butyl hydroperoxide and ascorbic acid are used for post-treatment reaction, and the temperature is kept for 20 minutes; the temperature is lowered to below 50 ° C and the material is discharged to obtain a hollow acrylic emulsion with a latex particle size of 450 nm and a shell thickness to hollow microsphere particle size ratio of 20:100.

[0078] The difference between the preparation method of the hollow acrylic emulsion with a latex particle size of 900 nm and the preparation method of the hollow acrylic emulsion with a latex particle size of 450 nm is that: in step (2), 1 part of an emulsifier, sodium dodecylbenzenesulfonate (DS-4), is dispersed in 16.44 parts of deionized water, and 21.38 parts of an olefin monomer, methyl methacrylate (MMA), and 11.51 parts of an unsaturated acid, methacrylic acid (MAA), are slowly added to the water under stirring; in step (3), a reaction flask is prepared, 23.68 parts of water are added thereto, and 20% of a pre-emulsion (a total of 50.33 parts of the pre-emulsion) is added; otherwise, the preparation method is the same as the preparation method of the hollow acrylic emulsion with a latex particle size of 450 nm, to obtain a hollow acrylic emulsion with a latex particle size of 900 nm and a shell thickness to hollow microsphere particle size ratio of 20:100.

[0079] The difference between the preparation method of the hollow acrylic emulsion with a latex particle size of 1700 nm and the preparation method of the hollow acrylic emulsion with a latex particle size of 450 nm is that: in step (2), 1 part of an emulsifier, sodium dodecylbenzenesulfonate (DS-4), is dispersed in 16.45 parts of deionized water, and 21.39 parts of an olefin monomer, methyl methacrylate (MMA), and 11.52 parts of an unsaturated acid, methacrylic acid (MAA), are slowly added to the water under stirring; in step (3), a reaction flask is prepared, 23.7 parts of water are added thereto, and 20% of a pre-emulsion (a total of 50.36 parts of the pre-emulsion) is added; 6.68 parts of a siloxane compound with an active group are added to a reactor at one time; the other steps are the same as the preparation method of the hollow acrylic emulsion with a latex particle size of 450 nm, to obtain a hollow acrylic emulsion with a latex particle size of 1700 nm and a shell thickness to hollow microsphere particle size ratio of 20:100.

[0080] Example 2

[0081] A reflective heat-insulating coating, comprising, by weight, 2 parts of a hollow acrylic emulsion A with a latex particle size of 600 nm, 3 parts of a hollow acrylic emulsion B with a latex particle size of 1000 nm, and 1 part of a hollow acrylic emulsion C with a latex particle size of 1600 nm. 5 parts, elastic acrylic emulsion 25 parts, filler 26 parts (calcite powder 5 parts, rutile titanium dioxide 20 parts, diatomaceous earth 1 part), nonionic alkyl polyoxyethylene ether wetting agent 0.4 parts, polyacrylate ammonium salt dispersant 0.6 parts, mineral oil defoamer 0.6 parts, thickener hydroxyethyl cellulose 0.3 parts, fungicide (a mixture of pyrimidine copper zinc and zinc oxide) 0.3 parts, preservative (a mixture of 5-chloro-2-methyl-4-isothiazoline-3-one and 2-methyl-4-isothiazoline-3-one), mildewproof agent 2-benzimidazole methyl carbamate 0.4 parts, pH adjuster 2-amino-2-methyl-1-propanol 0.1 parts, antifreeze-thaw aid propylene glycol 2 parts, film-forming aid dodecyl alcohol ester 0.5 parts, functional additive nonionic polyurethane leveling agent 2 parts, water 25 parts;

[0082] The latex particles in hollow acrylic emulsion A, hollow acrylic emulsion B, and hollow acrylic emulsion C are all hollow microspheres;

[0083] The ratio of the shell thickness to the particle size of the hollow microspheres of the three particle sizes is 20:100.

[0084] A method for preparing a reflective heat-insulating coating comprises the following steps:

[0085] Add water, a wetting agent, a dispersant, and 20% of a defoaming agent while stirring at 200 rpm, and stir for 3 minutes; adjust the speed to 400 rpm, add a thickener, and stir for 2 minutes; adjust the speed to 1200 rpm, add a filler, and stir for 15 minutes; adjust the speed to 900 rpm, add a film-forming agent, an antifreeze agent, and a bactericidal, mildew-proof, and preservative, and stir for 3 minutes; then add hollow acrylic emulsion A, hollow acrylic emulsion B, hollow acrylic emulsion C, and elastic acrylic emulsion, and stir for 3 minutes; add a functional additive and stir for 3 minutes; add the remaining defoaming agent, and stir evenly to prepare a reflective and heat-insulating coating.

[0086] The difference between the preparation method of the hollow acrylic emulsion with a latex particle size of 600 nm and the preparation method of the hollow acrylic emulsion with a latex particle size of 450 nm is that: in step (2), 1 part of the emulsifier sodium dodecylbenzenesulfonate (DS-4) is dispersed in 17.55 parts of deionized water, and 22.82 parts of the olefin monomer methyl methacrylate (MMA) and 12.29 parts of the unsaturated acid methacrylic acid (MAA) are slowly added to the above water under stirring; in step (3), a reaction flask is prepared, 25.25 parts of water are added thereto, and 20% of the pre-emulsion (a total of 53.66 parts of the pre-emulsion) is added; 4.45 parts of the siloxane compound with an active group are added to the reactor at one time; the other steps are the same as the preparation method of the hollow acrylic emulsion with a latex particle size of 450 nm, and a hollow acrylic emulsion with a latex particle size of 600 nm and a shell thickness to hollow microsphere particle size ratio of 20:100 is obtained.

[0087] The difference between the preparation method of the hollow acrylic emulsion with a latex particle size of 1000 nm and the preparation method of the hollow acrylic emulsion with a latex particle size of 450 nm is that: in step (2), 1 part of an emulsifier, sodium dodecylbenzenesulfonate (DS-4), is dispersed in 16.45 parts of deionized water, and 21.39 parts of an olefin monomer, methyl methacrylate (MMA), and 11.52 parts of an unsaturated acid, methacrylic acid (MAA), are slowly added to the water under stirring; in step (3), a reaction flask is prepared, 23.69 parts of water are added thereto, and 20% of a pre-emulsion (a total of 50.36 parts of the pre-emulsion) is added; 6.67 parts of a siloxane compound with an active group are added to a reactor at one time; the other steps are the same as the preparation method of the hollow acrylic emulsion with a latex particle size of 450 nm, to obtain a hollow acrylic emulsion with a latex particle size of 1000 nm and a shell thickness to hollow microsphere particle size ratio of 20:100.

[0088] The difference between the preparation method of the hollow acrylic emulsion with a latex particle size of 1600 nm and the preparation method of the hollow acrylic emulsion with a latex particle size of 450 nm is that: in step (2), 1 part of an emulsifier, sodium dodecylbenzenesulfonate (DS-4), is dispersed in 15.8 parts of deionized water, and 20.53 parts of an olefin monomer, methyl methacrylate (MMA), and 11.06 parts of an unsaturated acid, methacrylic acid (MAA), are slowly added to the water under stirring; in step (3), a reaction flask is prepared, 22.75 parts of water are added thereto, and 20% of a pre-emulsion (a total of 48.39 parts of the pre-emulsion) is added; 8.01 parts of a siloxane compound with an active group are added to a reactor at one time; in step (4), 22.61 parts of seed emulsion are added to 33.05 parts of water; an emulsion consisting of 0.46 parts of sodium dodecylbenzenesulfonate (DS-4), 19.7 parts of styrene (ST), 1.32 parts of methyl methacrylate (MMA), 0.04 parts of allyl methacrylate (AMA), 0.13 parts of methacrylic acid (MAA) and 15.68 parts of water and an aqueous solution of 0.07 parts of sodium persulfate and 0.36 parts of water are added dropwise; 0.66 parts of aqueous ammonia are added when the emulsion is added dropwise to 45%. Otherwise, the method is the same as that for preparing a hollow acrylic emulsion with a latex particle size of 450 nm, to obtain a hollow acrylic emulsion with a latex particle size of 1600 nm and a ratio of the thickness of the shell to the particle size of the hollow microspheres of 20:100.

[0089] Example 3

[0090] A reflective heat-insulating coating, comprising, by weight, 5 parts of a hollow acrylic emulsion A with a latex particle size of 700 nm, 3 parts of a hollow acrylic emulsion B with a latex particle size of 1100 nm, and 3 parts of a hollow acrylic emulsion C with a latex particle size of 1800 nm. 2 parts, elastic acrylic emulsion 25 parts, filler 26 parts (calcite powder 5 parts, rutile titanium dioxide 20 parts, diatomaceous earth 1 part), nonionic alkyl polyoxyethylene ether wetting agent 0.4 parts, polyacrylate ammonium salt dispersant 0.6 parts, mineral oil defoamer 0.6 parts, thickener hydroxyethyl cellulose 0.3 parts, fungicide (a mixture of pyrimidine copper zinc and zinc oxide) 0.3 parts, preservative (a mixture of 5-chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-4-isothiazolin-3-one), mildewproof agent 2-benzimidazole methyl carbamate 0.4 parts, pH adjuster 2-amino-2-methyl-1-propanol 0.1 parts, antifreeze-thaw aid propylene glycol 2 parts, film-forming aid dodecyl alcohol ester 0.5 parts, functional additive nonionic polyurethane leveling agent 2 parts, water 25 parts;

[0091] The latex particles in hollow acrylic emulsion A, hollow acrylic emulsion B, and hollow acrylic emulsion C are all hollow microspheres;

[0092] The ratio of the shell thickness to the particle size of the hollow microspheres of the three particle sizes is 20:100.

[0093] A method for preparing a reflective heat-insulating coating comprises the following steps:

[0094] Add water, wetting agent, dispersant, and 20% defoamer while stirring at 200 rpm, and stir for 3 minutes; adjust the speed to 400 rpm, add thickener, and stir for 2 minutes; adjust the speed to 1200 rpm, add titanium dioxide and filler, and stir for 15 minutes; adjust the speed to 900 rpm, add film-forming agent, antifreeze agent, bactericidal and mildew-proof preservative, and stir for 3 minutes; then add hollow acrylic emulsion A, hollow acrylic emulsion B, hollow acrylic emulsion C, and elastic acrylic emulsion, and stir for 3 minutes; add functional additives, and stir for 3 minutes; add the remaining defoamer, and stir evenly to prepare a reflective and heat-insulating coating.

[0095] The difference between the preparation method of the hollow acrylic emulsion with a latex particle size of 700 nm and the preparation method of the hollow acrylic emulsion with a latex particle size of 450 nm is that: in step (2), 1 part of the emulsifier sodium dodecylbenzenesulfonate (DS-4) is dispersed in 18.46 parts of deionized water, and 24 parts of olefin monomer methyl methacrylate (MMA) and 12.92 parts of unsaturated acid methacrylic acid (MAA) are slowly added to the above water under stirring; in step (3), a reaction flask is prepared, 26.58 parts of water are added thereto, and 20% of the pre-emulsion (a total of 56.38 parts of the pre-emulsion) is added; 2.81 parts of a siloxane compound with an active group are added to the reactor at one time; the other steps are the same as the preparation method of the hollow acrylic emulsion with a latex particle size of 450 nm, and a hollow acrylic emulsion with a latex particle size of 700 nm and a shell thickness to hollow microsphere particle size ratio of 20:100 is obtained.

[0096] The difference between the preparation method of the hollow acrylic emulsion with a latex particle size of 1100 nm and the preparation method of the hollow acrylic emulsion with a latex particle size of 450 nm is that: in step (2), 1 part of the emulsifier sodium dodecylbenzenesulfonate (DS-4) is dispersed in 16.8 parts of deionized water, 20.58 parts of olefin monomer methyl methacrylate (MMA) and 9.97 parts of unsaturated acid methacrylic acid (MAA) are slowly added to the above water under stirring. In step (3), a reaction flask is prepared, 22.75 parts of water are added thereto, and 20% of the pre-emulsion (a total of 48.35 parts of the pre-emulsion) is added; in step (4), 0.86 parts of ammonia water is added when the emulsion is added to 45%, and the rest is the same as the preparation method of the hollow acrylic emulsion with a latex particle size of 450 nm, to obtain a hollow acrylic emulsion with a latex particle size of 1100 nm and a shell thickness to hollow microsphere particle size ratio of 20:100.

[0097] The difference between the preparation method of the hollow acrylic emulsion with a latex particle size of 1800 nm and the preparation method of the hollow acrylic emulsion with a latex particle size of 450 nm is that in step (2), 1.07 parts of an emulsifier, sodium dodecylbenzenesulfonate (DS-4), is dispersed in 17.55 parts of deionized water, 22.82 parts of an olefin monomer, methyl methacrylate (MMA), and 12.29 parts of an unsaturated acid, methacrylic acid (MAA), are slowly added under stirring. In the above-mentioned water; in step (3), a reaction flask is prepared, 25.28 parts of water are added thereto, and 20% of the pre-emulsion (a total of 53.73 parts of the pre-emulsion) is added; 4.45 parts of the siloxane compound with an active group are added to the reactor at one time, and the rest is the same as the preparation method of the hollow acrylic emulsion with a latex particle size of 450nm, to obtain a hollow acrylic emulsion with a latex particle size of 1800nm and a shell thickness to hollow microsphere particle size ratio of 20:100.

[0098] Comparative Example 1

[0099] The only difference between Comparative Example 1 and Example 1 is that Comparative Example 1 uses equal amounts of water to replace hollow acrylic emulsion A, hollow acrylic emulsion B, and hollow acrylic emulsion C, that is, it does not contain hollow acrylic emulsion. Other aspects are the same as Example 1.

[0100] Comparative Example 2

[0101] The only difference between Comparative Example 2 and Example 1 is that Comparative Example 2 uses equal amounts of hollow polystyrene microspheres (ZPH-104 of Shanghai Zhenzhun Biotechnology Co., Ltd.) used in the prior art with publication number CN106867348A to replace the hollow acrylic emulsion A, hollow acrylic emulsion B, and hollow acrylic emulsion C in Example 1, and the rest is the same as Example 1.

[0102] Comparative Example 3

[0103] The only difference between Comparative Example 3 and Example 1 is that the ratio of the shell thickness of the hollow microspheres in Comparative Example 3 to the particle size of the hollow microspheres is 5:100, that is, the shell thickness of the hollow microspheres is reduced, and the rest is the same as Example 1.

[0104] Comparative Example 4

[0105] The only difference between Comparative Example 4 and Example 1 is that the ratio of the shell thickness of the hollow microspheres in Comparative Example 4 to the particle size of the hollow microspheres is 50:100, that is, the shell thickness of the hollow microspheres is increased, and the rest is the same as Example 1.

[0106] Comparative Example 5

[0107] The only difference between Comparative Example 5 and Example 1 is that Comparative Example 5 uses an equal amount of hollow acrylic emulsion B with a latex particle size of 900 nm to replace the hollow acrylic emulsion A with a particle size of 450 nm, that is, it does not contain hollow acrylic emulsion A. Other details are the same as Example 1.

[0108] Comparative Example 6

[0109] The only difference between Comparative Example 6 and Example 1 is that Comparative Example 6 uses an equal amount of hollow acrylic emulsion A with a latex particle size of 450 nm to replace an equal amount of hollow acrylic emulsion B with a latex particle size of 900 nm, that is, it does not contain hollow acrylic emulsion B. Other details are the same as Example 1.

[0110] Comparative Example 7

[0111] The only difference between Comparative Example 7 and Example 1 is that Comparative Example 7 uses an equal amount of hollow acrylic emulsion B with a latex particle size of 900 nm to replace the hollow acrylic emulsion C with a latex particle size of 1700 nm, that is, it does not contain hollow acrylic emulsion C, and the rest is the same as Example 1.

[0112] Performance Testing

[0113] The coatings prepared in Examples 1-3 and Comparative Examples 1-7 were applied to aluminum plates and then cured for 168 hours under standard conditions to obtain coatings with a thickness of 0.3 mm. Performance tests were then performed. The specific test items and test methods are as follows:

[0114] Test of thermal insulation performance of coating film: prepare a simple device for measuring thermal insulation performance of coating film: the heating light source is a 275W heating lamp, which is 25cm away from the coating film. Except for the position where the test sample is placed at the top of the measuring chamber, the rest of the room can be regarded as insulated. The thermometer shows the temperature inside the measuring chamber (polystyrene foam box). The schematic diagram of the thermal insulation performance test device is as follows: Figure 1 The experiment simulates the indoor temperature conditions corresponding to different exterior wall coatings under sunlight. The room temperature is controlled at 25°C, equivalent to the constant ambient temperature of the building. The test sample plate is equivalent to the exterior wall coated with thermal insulation coating. The temperature test is conducted in the test chamber that simulates indoor temperature changes. During the experiment, the test sample plate is sealed with the test chamber, and the heating lamp is powered on until the temperature stabilizes. The final temperature in the test chamber is recorded for comparison of thermal insulation performance.

[0115] Solar reflectance: tested in accordance with GB / T 25261-2018;

[0116] Near-infrared reflectance: tested in accordance with GB / T 25261-2018;

[0117] Hemispherical emissivity: tested in accordance with GB / T 25261-2018;

[0118] Stain resistance: Tested in accordance with GB / T 9755-2014;

[0119] Tensile strength: Tested in accordance with JG / T172-2014;

[0120] Elongation at break (under standard conditions): Tested in accordance with JG / T172-2014;

[0121] Artificial aging resistance: Tested in accordance with JG / T172-2014.

[0122] The performance test results of the coatings prepared in Examples 1-3 and Comparative Examples 1-7 are shown in Table 1.

[0123] Table 1: Performance test results of coatings prepared in Examples 1-3 and Comparative Examples 1-7

[0124]

[0125] As can be seen from Table 1, the reflective heat-insulating coating prepared by the present invention has good reflective heat-insulating effect, the lowest temperature in the test room is 30.2° C., and it has good mechanical properties, stain resistance, and artificial aging resistance.

[0126] Comparative Example 1 does not contain hollow acrylic emulsion, so the reflective heat insulation effect, mechanical properties, stain resistance, and artificial aging resistance of the coating prepared in Comparative Example 1 are significantly worse than those in Example 1, and the final temperature in the test chamber is 11.8°C higher than that in Example 1.

[0127] Comparative Example 2 uses hollow polystyrene microspheres, so the reflective heat insulation effect, mechanical properties, stain resistance, and artificial aging resistance of the coating prepared in Comparative Example 2 are significantly worse than those in Example 1, and the final temperature in the test chamber is 7.7°C higher than that in Example 1.

[0128] The shell thickness in Comparative Example 3 is thinner, and the shell thickness in Comparative Example 4 is thicker, so that the reflective heat insulation effect, mechanical properties, and stain resistance of the coatings prepared in Comparative Examples 3 and 4 are worse than those in Example 1, and the artificial aging resistance of Comparative Example 3 is also poor. The final temperatures in the test chambers of Comparative Examples 3-4 are 9.9°C and 7.2°C higher than those in Example 1, respectively.

[0129] Comparative Example 5 does not contain hollow acrylic emulsion A, Comparative Example 6 does not contain hollow acrylic emulsion B, and Comparative Example 7 does not contain hollow acrylic emulsion C, so that Comparative Examples 5-7 cannot achieve the compounding of hollow microspheres of three particle sizes, and thus their reflective heat insulation effects, mechanical properties, and stain resistance are all worse than those of Example 1. The final temperatures in the test chambers of Comparative Examples 5-7 are 6.7°C, 6.1°C, and 7.3°C higher than those of Example 1, respectively.

[0130] In summary, the present invention utilizes a composite of three hollow acrylic emulsions with different particle size ranges, resulting in a synergistic effect between the hollow microspheres of different sizes. Furthermore, the shell and particle size of the hollow microspheres exhibit a specific size relationship, which benefits the coating's reflective thermal insulation properties, mechanical properties, stain resistance, and weather resistance. The reflective and thermal insulation coating of the present invention exhibits a solar reflectance of up to 0.88, a near-infrared reflectance of up to 0.9, and a hemispherical emissivity of up to 0.93. Compared to Comparative Example 1, the final temperature within the test chamber can be reduced by 11.8°C. The coating also exhibits a tensile strength of up to 2.89 MPa and an elongation at break of up to 507%, demonstrating its significant potential for application in building walls.

[0131] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A coating, characterized in that: Including hollow acrylic emulsion A, hollow acrylic emulsion B, hollow acrylic emulsion C, elastic acrylic emulsion; The particle sizes of the latex particles in the hollow acrylic emulsion A, the hollow acrylic emulsion B, and the hollow acrylic emulsion C are 450-750 nm, 900-1300 nm, and 1400-1800 nm, respectively; The latex particles in the hollow acrylic emulsion A, the hollow acrylic emulsion B, and the hollow acrylic emulsion C are all hollow microspheres; the hollow microspheres include a shell layer; the ratio of the thickness of the shell layer to the particle size of the hollow microspheres is (9-33):100; In the coating, the hollow acrylic emulsion A, the hollow acrylic emulsion B, and the hollow acrylic emulsion C are all 1.8-11 parts by weight, and the elastic acrylic emulsion is 18-33 parts; The preparation methods of the hollow acrylic emulsion A, the hollow acrylic emulsion B, and the hollow acrylic emulsion C all comprise the following steps: S1: reacting an emulsifier, an unsaturated acid, an olefin monomer, an initiator, a silicone compound with an active group, and water to prepare a seed emulsion; S2: reacting an emulsifier, an unsaturated acid, an olefin monomer, an initiator, water and the seed emulsion obtained in step S1 to prepare the hollow acrylic emulsion A, the hollow acrylic emulsion B or the hollow acrylic emulsion C.

2. The coating according to claim 1, characterized in that The solid content of the elastic acrylic emulsion is 45-60%.

3. The coating according to claim 1, characterized in that The particle size of the latex particles in the elastic acrylic emulsion is 90-330 nm.

4. The coating according to any one of claims 1 to 3, characterized in that The coating further comprises at least one of a filler, a wetting agent, a dispersant, a defoaming agent, a thickener, a bactericide, a preservative, a mildew preventer, a pH regulator, an antifreeze-thaw aid, a film-forming aid, a functional aid, and water.

5. The coating according to claim 4, characterized in that The coating comprises hollow acrylic emulsion A, hollow acrylic emulsion B, hollow acrylic emulsion C, elastic acrylic emulsion, filler, wetting agent, dispersant, defoamer, thickener, bactericide, preservative, mildewproof agent, pH regulator, antifreeze-thaw aid, film-forming aid, functional additive, and water; and by weight, the coating comprises 1.8-11 parts of hollow acrylic emulsion A, 1.8-11 parts of hollow acrylic emulsion B, and 1.8-11 parts of hollow acrylic emulsion C. 1.8-11 parts, elastic acrylic emulsion 18-33 parts, filler 23-40 parts, wetting agent 0.27-0.55 parts, dispersant 0.55-1.2 parts, defoaming agent 0.55-1.1 parts, thickener 0.27-0.55 parts, bactericide 0.1-0.33 parts, preservative 0.18-0.33 parts, mildewproof agent 0.18-0.44 parts, pH adjuster 0.1-0.22 parts, antifreeze-thaw aid 0.9-2.2 parts, film-forming aid 0.45-1.1 parts, functional additive 0.9-2.2 parts, water 20-25 parts.

6. The coating according to claim 4, characterized in that The filler comprises at least one of calcite powder, diatomaceous earth and titanium dioxide; And / or, the wetting agent includes at least one of an anionic wetting agent and a nonionic wetting agent; and / or, the dispersant comprises at least one of polycarboxylates, polyacrylates, and carboxylic acid copolymer salts; And / or, the defoaming agent includes at least one of polymer composite mineral oil, metal soap defoaming agent, and silicone defoaming agent; and / or, the thickener comprises hydroxyethyl cellulose; and / or, the fungicide comprises at least one of pyrimidine copper zinc and zinc oxide; And / or, the preservative includes at least one of 5-chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-4-isothiazolin-3-one; and / or, the mildewcide comprises methyl 2-benzimidazolecarbamate; and / or, the pH adjuster comprises 2-amino-2-methyl-1-propanol; and / or, the antifreeze-thaw aid comprises propylene glycol; and / or, the film-forming aid comprises lauryl alcohol ester; And / or, the functional auxiliary agent includes a non-ionic polyurethane leveling modifier.

7. The method for preparing the coating according to any one of claims 1 to 6, characterized in that: The following steps are involved: The coating is prepared by mixing various raw material components.

8. The preparation method according to claim 7, characterized in that The following steps are involved: (1) dissolving the dispersant and wetting agent in water, adding the thickener, and then adding the pH adjuster and filler, and mixing to obtain a premix; (2) Mixing the remaining components with the premix obtained in step (1) to prepare the coating.

9. Use of the coating according to any one of claims 1 to 6 in the field of construction.

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