Reflective heat-insulation water-based polyurea coating and preparation method thereof

Abstract

The invention discloses a reflective heat-insulation water-based polyurea coating and a preparation method thereof. The reflective heat-insulation water-based polyurea coating is prepared from the following components: modified water-based polyurea resin, deionized water, a wetting dispersant, a defoaming agent, a reflective filler, a heat-insulation filler, a coalescing agent, an anti-flash-rust agent, a flatting agent and a thickening agent. The reflective filler is zinc titanate; the modified water-based polyurea resin is obtained by grafting hollow polystyrene-b-polyacrylamide microspheres on water-based polyurea resin; the hollow polystyrene-b-polyacrylamide microsphere is prepared by the following steps: firstly, preparing a prepolymer by adopting an emulsion polymerization method, then preparing a core-shell microsphere which takes the prepolymer as an inner shell and polystyrene-b-polyacrylamide as an outer shell by adopting a seed emulsion polymerization method, and finally, removing an inner core in the core-shell microsphere by adopting an alkali swelling method. The reflective heat-insulation water-based polyurea coating disclosed by the invention has excellent heat insulation performance and can be widely applied to the field of building heat insulation.

Description

Technical Field

[0001] The invention relates to a reflective heat-insulating water-soluble polyurea coating and a preparation method thereof, belonging to the technical field of building heat insulation. Background Art

[0002] With further urbanization, active cooling in building insulation consumes more and more energy. How to better save energy and reduce emissions and reduce energy consumption is an urgent problem to be solved. Thermal insulation coating refers to a recently developed functional water-based coating that can block, reflect, and radiate near-infrared heat from sunlight. It can insulate and cool the roof, save energy, and reduce consumption. It is currently widely used in the field of building insulation.

[0003] Traditional building thermal insulation coatings are mainly solvent-based coatings. During the coating process, a large amount of volatilization seriously pollutes the air quality. At the same time, it wastes production raw materials and causes serious pollution during the production process, which is not in line with the current green environmental protection concept. Water-based coatings are widely used in building and automotive coatings because they are green and environmentally friendly and meet the requirements of low volatile organic compound emissions. However, traditional water-based coatings still have some defects. They usually contain a large number of hydrophilic groups and surfactants, and a large number of microporous channels are formed after film formation. H2O, O2 and Cl in the corrosive medium - It will slowly penetrate and cannot provide long-term corrosion protection for the building's exterior walls.

[0004] In addition, for building insulation, the coating formed by the existing water-based thermal insulation coating only has the function of blocking heat insulation, with low thermal insulation efficiency and weak anti-corrosion and waterproofing effects. Some thermal insulation coatings may lose their effectiveness under long-term ultraviolet radiation or severe weather conditions, resulting in reduced thermal insulation performance. At the same time, the greenhouse effect has led to rising global temperatures, and the impact of the heat island effect has also caused the existing building thermal insulation coatings to fail to meet the living needs of residents.

[0005] Reflective thermal insulation coatings are made of synthetic resin as the base material, functional pigments, fillers and additives, and have high solar reflectance, near-infrared reflectance and hemispherical emissivity. Reflective thermal insulation coatings have the dual functions of decoration and thermal insulation, and are functional coatings. Since reflective thermal insulation coatings can significantly reduce the surface temperature of objects exposed to solar thermal radiation, this type of coating has rapidly expanded from the aerospace industry to the petrochemical industry, grain reserve industry, etc. Compared with thermal insulation coatings, reflective thermal insulation coatings have lower costs, better cooling effects, and also have anti-corrosion and waterproof properties. At present, reflective thermal insulation coatings have begun to be used in construction projects for reflective thermal insulation of roofs and walls, and have a trend of rapid growth.

[0006] The resin and filler used in reflective thermal insulation coatings have a significant impact on the performance of the coatings. Polyurea resin has good anti-corrosion, waterproof, wear-resistant and other properties. It is also highly durable and can resist erosion from various natural factors and external environments, including ultraviolet radiation, temperature changes, chemical corrosion, etc. Polyurea resin also has good thermal stability and chemical stability, can withstand high temperatures up to 350°C, and has good resistance to alkali, acid, solvents and natural aging. At present, polyurea resin has been widely used in reflective thermal insulation coatings. The fillers of reflective thermal insulation coatings are mainly divided into reflective fillers and thermal insulation fillers from the functional point of view. Among them, reflective fillers use the reflective function of fillers to reflect sunlight in the visible light region and near-infrared region, and prevent the heat of sunlight from accumulating and heating on the surface of the object, thereby achieving the effect of reflective insulation; thermal insulation fillers mainly form a dense vacuum layer on the surface of the coated object, which can effectively block the conduction of solar radiation heat and thermal radiation in the air, reduce the heat exchange between the inside and outside of the coated object, and thus achieve the effect of blocking insulation.

[0007] At present, there have been reports on reflective heat-insulating polyurea coatings, such as patents CN103214921A and CN107603440A, which disclose reflective heat-insulating polyurea coatings. However, the resins used in the currently disclosed reflective heat-insulating polyurea coatings are all conventional polyurea resins, and the reflective fillers used are mainly titanium dioxide, resulting in that the thermal insulation performance of the current reflective heat-insulating polyurea coatings cannot well meet the requirements of building heat insulation. Summary of the invention

[0008] In view of the above problems existing in the prior art, the object of the present invention is to provide a reflective water-insulating polyurea coating and a preparation method thereof.

[0009] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is as follows:

[0010] A reflective water-insulating polyurea coating having the following composition and proportion:

[0011] Modified waterborne polyurea resin: 45-55 parts by mass;

[0012] Deionized water: 15-20 parts by weight;

[0013] Wetting and dispersing agent: 0.3-0.6 parts by mass;

[0014] Defoaming agent: 0.05-0.35 parts by mass;

[0015] Reflective filler: 10-15 parts by mass;

[0016] Thermal insulation filler: 15-25 parts by mass;

[0017] Film-forming aid: 0.05-2 parts by mass;

[0018] Anti-flash rust agent: 0.1-0.4 parts by mass;

[0019] Leveling agent: 0.5-2 parts by mass;

[0020] pH adjuster: 0.01-0.05 parts by weight;

[0021] Thickener: 0.4-1 parts by mass;

[0022] The reflective filler is zinc titanate;

[0023] The modified waterborne polyurea resin is obtained by grafting hollow polystyrene-b-polyacrylamide microspheres onto waterborne polyurea resin; the hollow polystyrene-b-polyacrylamide microspheres are firstly prepared by emulsion polymerization for preparing prepolymer, then prepared by seed emulsion polymerization for preparing core-shell microspheres with prepolymer as inner shell and polystyrene-b-polyacrylamide as outer shell, and finally obtained by removing the inner core of the core-shell microspheres by alkali swelling method.

[0024] In one embodiment, the thermal insulation filler is any one of hollow glass microspheres, nano aerogels (e.g., silica nano aerogels), and a mixture of hollow glass microspheres and nano aerogels. When the thermal insulation filler is a mixture of hollow glass microspheres and nano aerogels, the mass ratio of hollow glass microspheres to nano aerogels is (15-25):1.

[0025] In one embodiment, the wetting and dispersing agent is any one of acrylic acid (for example, EFKA-4570), alkylhydroxyl ammonium salt (for example, BYK-180), and a mixture of high molecular weight carboxylic acid and modified polysiloxane.

[0026] In one embodiment, the defoaming agent is any one of silicone (eg, Dow Corning DC-62), polyether (eg, BYK-019), and polyether-modified silicone.

[0027] In one embodiment, the film-forming aid is any one of alcohols, alcohol esters (eg, dodecyl alcohol ester, propylene glycol diacetate), and alcohol ethers.

[0028] In one embodiment, the anti-flash rust agent is any one of an organic amine salt complex, phthalimide, and benzopyrimidine.

[0029] In one embodiment, the leveling agent is a silicone leveling agent, such as BYK-3455, BYK34, and BYK349.

[0030] In one embodiment, the pH adjuster is any one of Dow AMP-95, ammonia water, and KOH.

[0031] In one embodiment, the thickener is any one of cellulose ethers (eg, sodium carboxymethyl cellulose), polyacrylates, and polyacrylamides.

[0032] In one embodiment, the preparation of the modified waterborne polyurea resin comprises the following steps:

[0033] a) Under nitrogen protection, first add diisocyanate to the reactor, then add polyetheramine dropwise to the reactor at 40-50°C (drop rate is 3-7 seconds / drop), after the dropwise addition, heat-insulate and stir to react for 15-25 minutes; then disperse hollow polystyrene-b-polyacrylamide microspheres in an organic solvent to obtain a microsphere dispersion, and add the obtained microsphere dispersion to the reactor; then heat-insulate and stir to react the obtained reaction system for 2-3 hours

[0034] b) raising the temperature to 80-90° C., adding a hydrophilic chain extender, and stirring for 2-3 hours to obtain a polyurea prepolymer;

[0035] c) cooling to 70-80° C., adding a crosslinking agent, and stirring for 1-1.5 hours to obtain a crosslinked product;

[0036] d) cooling to 40-50° C., adding a neutralizing agent, keeping the temperature for reaction for 20-40 minutes, adding deionized water for dispersion for 2-3 hours, and then placing the obtained product in a vacuum drying oven for degassing to obtain the modified waterborne polyurea resin (the solid content of the modified waterborne polyurea resin is 40-45%).

[0037] A preferred embodiment, in the preparation process of the modified waterborne polyurea resin, the mass ratio of hollow polystyrene-b-polyacrylamide microspheres: hydrophilic chain extender: cross-linking agent: neutralizer: (diisocyanate + polyetheramine) is (0.01-0.08): (1.1-1.2): (0.25-0.3): (0.7-0.8): (27.5-28.5); the molar ratio of diisocyanate: polyetheramine is (2-4): (0.9-1.1).

[0038] In a preferred embodiment, in step a), the diisocyanate is any one of isophorone diisocyanate, hexamethylene diisocyanate and diphenylmethane diisocyanate.

[0039] In a preferred embodiment, in step a), the organic solvent used in the microsphere dispersion is selected from any one of acetone, tetrahydrofuran, and N,N-dimethylformamide; in the microsphere dispersion, the mass ratio of organic solvent: hollow polystyrene-b-polyacrylamide microspheres is (20-30):0.06.

[0040] In a preferred embodiment, in step b), the hydrophilic chain extender is any one of dihydroxymethylbutyric acid, N-methyldiethanolamine, and diethanolamine.

[0041] In a preferred embodiment, in step c), the cross-linking agent is any one of trimethylolpropane, ethylene glycol, 1,4-butanediol and dipropylene glycol.

[0042] In a preferred embodiment, in step d), the neutralizing agent is any one of hydrochloric acid, acetic acid, chlorinated hydrocarbon, and triethylamine.

[0043] In one embodiment, the hollow polystyrene-b-polyacrylamide microspheres are prepared by first preparing a suspension of an acrylate prepolymer by an emulsion polymerization method, and then using the acrylate prepolymer as the core, a block polymer layer of styrene and acrylamide is formed on the surface of the acrylate prepolymer by a seed emulsion polymerization method to obtain core-shell microspheres with the acrylate prepolymer as the inner shell and the polystyrene-b-polyacrylamide as the outer shell, and finally removing the inner core of the core-shell microspheres by an alkali swelling method using ammonia water, collecting the solid product, and obtaining the hollow polystyrene-b-polyacrylamide microspheres.

[0044] In a preferred embodiment, the preparation of the hollow polystyrene-b-polyacrylamide microspheres comprises the following steps:

[0045] 1) First, α-methacrylic acid, hydroxyethyl methacrylate and methyl methacrylate are added into a reactor, stirred to mix evenly, then sodium dodecylbenzene sulfonate and deionized water are added, stirred to mix evenly, then an aqueous solution of ammonium persulfate is added dropwise at 85-90°C, and the mixture is stirred and reacted for 80-90 minutes to obtain a suspension emulsion of an acrylate prepolymer, referred to as a core emulsion;

[0046] 2) Add a certain amount of the core emulsion prepared in step 1) into the reactor, add sodium dodecylbenzene sulfonate, styrene and deionized water, stir to mix evenly, then drop an aqueous solution of ammonium persulfate at 80-90° C., after the dropwise addition, stir and react for 30 minutes under heat preservation, then add acrylamide, and continue to stir and react for 30 minutes under heat preservation;

[0047] 3) Raise the temperature to 90-95° C., add an oxidation-reduction initiation system consisting of an oxidant and a reductant, then drop ammonia water to adjust the pH to 9, then keep the mixture warm and stir for 150-160 minutes, and finally collect the solid product to obtain the hollow polystyrene-b-polyacrylamide microspheres.

[0048] In a preferred embodiment, during the preparation of hollow polystyrene-b-polyacrylamide microspheres, the stirring rate of the reaction system is 220-290 r / min, with 220-230 r / min being the best.

[0049] In a preferred embodiment, in step 1), the concentration of the ammonium persulfate aqueous solution is 0.020-0.021 g / mL; the mass ratio of α-methylacrylic acid: hydroxyethyl methacrylate: methyl methacrylate: sodium dodecylbenzenesulfonate: ammonium persulfate: deionized water is (18-19): (2.4-2.5): (0.5-0.6): (0.5-0.6): (0.20-0.21): 100.

[0050] In a preferred embodiment, in step 2), the concentration of the ammonium persulfate aqueous solution is 0.020-0.021 g / mL; the mass ratio of core emulsion: styrene: acrylamide: sodium dodecylbenzene sulfonate: ammonium persulfate: deionized water is (24-26): 11.5: 2.22: (0.04-0.05): (0.20-0.21): (12-14).

[0051] In a preferred embodiment, in step 3), the oxidation-reduction initiation system is any one of tert-butyl hydroperoxide-sodium formaldehyde sulfoxylate, potassium persulfate-sodium sulfite, and tert-butyl hydroperoxide-ascorbic acid, and the mass ratio of oxidant:reductant in the oxidation-reduction initiation system is 2:1.

[0052] In a preferred embodiment, in step 3), the operation of collecting the solid product is as follows:

[0053] After the reaction is completed, the reaction solution is centrifuged, and the separated precipitate is washed and filtered with ethanol and deionized water for 3 to 4 times, respectively. The filtered product is freeze-dried under vacuum to a constant weight.

[0054] In one embodiment, the preparation of zinc titanate comprises the following steps:

[0055] Equal amounts of nano-titanium dioxide and nano-zinc oxide powder are fully mixed in a ball mill, placed in a crucible, and then placed in a muffle furnace for calcination (calcination temperature is 850-950°C, calcination time is 20-28 hours). The calcined product is crushed, ground, and sieved. The obtained product powder is added to a silane modification liquid for modification treatment (stirring at room temperature for 1-2 hours). The obtained product is filtered, washed, dried, ground, and sieved to obtain the zinc titanate.

[0056] In a preferred embodiment, the silane-modified liquid is composed of a silane coupling agent, water and ethanol, wherein the mass ratio of silane coupling agent: water: ethanol is (0.5-1): (3.44-3.55): (30.96-31.95); the mass ratio of silane coupling agent: product powder is (4-5): 100.

[0057] In a preferred embodiment, the silane coupling agent is any one of KH-550, KH-560 and KH-570.

[0058] A method for preparing a reflective water-insulating polyurea coating comprises the following steps:

[0059] ① Add the proportion of deionized water, wetting dispersant and defoaming agent into the reactor and stir to mix them evenly;

[0060] ② Add the proportion of reflective filler and heat-insulating filler, and stir to mix them evenly;

[0061] ③ Add the modified waterborne polyurea resin and film-forming aid in a certain proportion, and stir to mix them evenly;

[0062] ④Add the proportion of anti-flash rust agent and leveling agent, and stir to mix evenly;

[0063] ⑤ Add a proportion of pH adjuster, stir to mix evenly, and make the pH of the resulting mixed liquid reach 9;

[0064] ⑥ Add a proportion of thickener and stir to mix evenly to obtain the reflective water-insulating polyurea coating.

[0065] Compared with the prior art, the present invention has the following significant beneficial effects:

[0066] The present invention uses a modified waterborne polyurea resin grafted with hollow polystyrene-b-polyacrylamide microspheres as a base resin and zinc titanate as a reflective filler, so that the reflective waterborne polyurea coating of the present invention has excellent thermal insulation performance, can be widely used in the field of building thermal insulation, and has good application value; in addition, the preparation method of the present invention is economical and practical, the preparation process is simple, the cost is low, no special equipment and harsh conditions are required, and large-scale production is easy to achieve, and it has extremely strong industrial application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 is a transmission electron micrograph of the hollow polystyrene-b-polyacrylamide microspheres prepared in Example 1 of the present invention;

[0068] Figure 2 is an infrared spectrum of the modified waterborne polyurea resin modified by hollow polystyrene-b-polyacrylamide microspheres prepared in Example 1 of the present invention;

[0069] Figure 3 The ultraviolet reflectivity graph of the thermal insulation filler zinc titanate prepared in Example 1 of the present invention and the traditional thermal insulation filler titanium dioxide;

[0070] Figure 4 This is the XRD pattern of the thermal insulation filler zinc titanate prepared in Example 1 of the present invention;

[0071] Figure 5 This is a transmission electron micrograph of the hollow polystyrene-b-polyacrylamide microspheres prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0072] The technical scheme of the present invention is further described in detail and completely below in conjunction with the examples. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. The experimental methods in the following examples without specifying specific conditions are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer.

[0073] Example 1

[0074] 1. Preparation of hollow polystyrene-b-polyacrylamide microspheres

[0075] 1) First, 2.5g of α-methacrylic acid, 0.5g of hydroxyethyl methacrylate and 18.5g of methyl methacrylate were added into a flask, stirred to mix evenly, then 0.5g of sodium dodecylbenzene sulfonate and 100g of deionized water were added, stirred to mix evenly, and then 10mL of 0.021g / mL ammonium persulfate aqueous solution was dropped into the flask at 90°C, and the mixture was stirred and reacted for 80 minutes to obtain a suspension emulsion of acrylate prepolymer, referred to as core emulsion; during the whole reaction process, the stirring rate was 220-230 r / min;

[0076] 2) Weigh 25 g of the core emulsion prepared in step 1) and add it to a flask (the core emulsion here is equivalent to the seed in the seed emulsion polymerization method), then add 0.04 g of sodium dodecylbenzene sulfonate, 11.5 g of styrene and 14 g of deionized water, stir to mix evenly, then drop 10 mL of 0.208 g / mL ammonium persulfate aqueous solution at 90°C, after the drop is completed, keep warm and stir to react for 30 minutes, then add 2.22 g of acrylamide, continue to keep warm and stir to react for 30 minutes, so that a block polymer layer of styrene and acrylamide can be formed on the surface of the acrylate prepolymer, so that the obtained reaction solution contains core-shell microspheres with the acrylate prepolymer as the inner shell and polystyrene-b-polyacrylamide as the outer shell; during the whole reaction process, the stirring rate is 220-230 r / min;

[0077] 3) The temperature was raised to 95°C, and an oxidation-reduction initiation system consisting of 0.14 g potassium persulfate and 0.07 g sodium sulfite (for monomer elimination) was added. Ammonia water was then added dropwise to adjust the pH to 9. The mixture was stirred and reacted for 160 minutes (stirring rate was 220-230 r / min). The reaction was terminated to obtain a homogeneous emulsion-like reaction solution. The reaction solution was centrifuged and the separated precipitate was washed and filtered with ethanol and deionized water for 3-4 times. The filtered product was freeze-dried under vacuum to a constant weight to obtain powdered hollow polystyrene-b-polyacrylamide microspheres.

[0078] 2. Preparation of modified waterborne polyurea resin

[0079] a) nitrogen was introduced into a three-necked flask equipped with a constant pressure funnel, a mechanical stirrer, a constant temperature water bath and a spherical condenser for 15 minutes, so that the subsequent reaction system in the three-necked flask was under a nitrogen protection atmosphere, 7.0 g of diphenylmethane diisocyanate (Mn = 250.24, 0.0280 mol) was first added to the flask, and then 27.7 g of polyetheramine D2000 (Mn = 1000, 0.0157 mol) was added dropwise to the flask at 45°C (the dropping rate was 7 seconds / drop). After the dropping was completed, the reaction was stirred and kept warm; then 0 .06 g of hollow polystyrene-b-polyacrylamide microspheres are dispersed in 2.1 g of acetone, and ultrasonically dispersed for 15 minutes to obtain a microsphere dispersion liquid, and the obtained microsphere dispersion liquid is added to a flask (the microsphere dispersion liquid can be prepared in advance, or it can be prepared on-site after adding diphenylmethane diisocyanate and polyetheramine. In this embodiment, the microsphere dispersion liquid is prepared on-site, and ultrasonically dispersed for 15 minutes to obtain the microsphere dispersion liquid, which is equivalent to stirring and reacting the mixture of diphenylmethane diisocyanate and polyetheramine for 15 minutes); and then the obtained reaction system is kept warm and stirred for 2.5 hours;

[0080] b) heating to 80° C., adding 1.12 g of dimethylolbutyric acid as a hydrophilic chain extender, and stirring for 2.5 hours to obtain a polyurea prepolymer;

[0081] c) cooling to 70° C., adding 0.28 g of dimethylolpropane, and reacting with stirring for 1 hour to obtain a cross-linked product;

[0082] d) Cooling to 50°C, adding 0.765 g of triethylamine, keeping the temperature for reaction for 30 minutes, then adding 50 mL of deionized water under high-speed shearing conditions for dispersion for 3 hours, and placing the obtained product in a vacuum drying oven for degassing (to remove residual organic solvent and bubbles) to obtain a modified waterborne polyurea resin with a solid content of 35%.

[0083] 3. Preparation of thermal insulation filler zinc titanate

[0084] 81.39g of nano-titanium dioxide and 79.87g of nano-zinc oxide powder (the molar ratio of nano-titanium dioxide: nano-zinc oxide is 1:1) are weighed, fully mixed in a ball mill and placed in a crucible, and the crucible is placed in a muffle furnace and calcined at 900°C for 24 hours. The calcined product is crushed, ground, and sieved to obtain a product powder; 0.71g of KH-550, 3.55g of deionized water, and 31g of ethanol are weighed and mixed to prepare a silane-modified liquid; 14.2g of the product powder is added to the silane-modified liquid, and stirred at room temperature for 1 hour at a stirring speed of 300r / min. The obtained product is filtered, washed, dried, ground, and sieved to obtain a thermal insulation filler zinc titanate.

[0085] 4. Preparation of zinc titanate reflective heat insulation modified waterborne polyurea coating

[0086] ① Add 20g of deionized water, 0.35g of wetting and dispersing agent EFKA-4570 and 0.25g of defoaming agent DC-62 into the reactor and stir to mix evenly;

[0087] ② Add 10g zinc titanate powder, 19g hollow glass microspheres and 1g silica nanoaerogel, and stir to mix evenly;

[0088] ③ Add 45g of modified waterborne polyurea resin and 0.05g of film-forming aid dodecanoate, and stir to mix evenly;

[0089] ④ Add 0.25g of anti-flash rust agent phthalimide and 0.5g of leveling agent BYK349, and stir to mix evenly;

[0090] ⑤ Add 0.4 g of ammonia water as a pH adjuster, stir to mix evenly, and make the pH of the resulting mixed liquid reach 9;

[0091] ⑥ Add 1g of thickener sodium carboxymethyl cellulose and stir to mix evenly to obtain the reflective heat-insulating water-based polyurea coating. This coating is called zinc titanate reflective heat-insulating modified water-based polyurea coating.

[0092] Figure 1 is a transmission electron micrograph of the hollow polystyrene-b-polyacrylamide microspheres prepared in this example; Figure 1 It can be seen that the microspheres prepared in this embodiment are hollow spherical. After testing, the size of the microspheres prepared in this embodiment is 150-160 nm.

[0093] Figure 2 is an infrared spectrum of the modified waterborne polyurea resin modified with hollow polystyrene-b-polyacrylamide microspheres prepared in this example; Figure 2 It can be seen that at 1466cm -1The stretching vibration peaks between the benzene ring and the vinyl group in the microspheres appeared at 1000-1600 cm -1 The benzene ring vibration peak appeared in the region, and at 2274 cm -1 There is no characteristic absorption peak of -NCO in the unmodified waterborne polyurea resin nearby, which indicates that the microspheres in this embodiment have reacted with the waterborne polyurea resin and have been successfully grafted onto the polyurea resin to form a modified waterborne polyurea resin.

[0094] Figure 3 The ultraviolet reflectivity graph of the thermal insulation filler zinc titanate prepared in this embodiment and the traditional thermal insulation filler titanium dioxide; Figure 3 It can be seen that the zinc titanate prepared in this embodiment has a higher reflectivity and better reflective heat insulation performance than the traditional thermal insulation filler titanium dioxide.

[0095] Figure 4 : This is the XRD pattern of the thermal insulation filler zinc titanate prepared in this example; the XRD pattern of zinc titanate is consistent with the standard spectrum, indicating that zinc titanate was successfully prepared.

[0096] The heat insulation performance of the zinc titanate reflective heat insulation modified waterborne polyurea coating prepared in this embodiment was tested, and the test method is as follows:

[0097] 1) Thermal insulation temperature difference test: The surface of the stainless steel sheet was polished with 400-mesh sandpaper, and then ultrasonically treated with ethanol to remove impurities on the surface; the treated iron sheet surface was used as the wet film coating surface, and the coating was prepared using a wet film preparation device with a coating thickness of 250 μm on the wet film preparation device; finally, the coating was dried at room temperature for 1 hour and dried in a 90°C forced air oven for 3 hours to obtain a reflective insulating water-soluble polyurea coating, and the coating was subjected to a thermal insulation temperature difference test. The test results are shown in Table 1;

[0098] 2) Thermal conductivity test: The zinc titanate reflective thermal insulation modified waterborne polyurea coating was dripped into a cylindrical coating mold through a straw, dried at room temperature for 1 hour, and dried in a 90°C forced air oven for 3 hours to obtain a zinc titanate reflective thermal insulation modified waterborne polyurea circular coating. The coating was tested for thermal conductivity. The test results are shown in Table 2.

[0099] Example 2

[0100] 1. Preparation of hollow polystyrene-b-polyacrylamide microspheres

[0101] 1) First, 2.4g of α-methacrylic acid, 0.55g of hydroxyethyl methacrylate and 19g of methyl methacrylate were added into a flask, stirred to mix evenly, then 0.6g of sodium dodecylbenzene sulfonate and 100g of deionized water were added, stirred to mix evenly, and then 10mL of 0.021g / mL ammonium persulfate aqueous solution was dropped at 90°C. After the dropping was completed, the mixture was stirred and reacted for 80 minutes to obtain a suspension emulsion of acrylate prepolymer, referred to as core emulsion; during the entire reaction process, the stirring rate was 280-290 r / min;

[0102] 2) Weigh 25 g of the core emulsion prepared in step 1) and add it to a flask (the core emulsion here is equivalent to the seed in the seed emulsion polymerization method), then add 0.05 g of sodium dodecylbenzene sulfonate, 11.5 g of styrene and 14 g of deionized water, stir to mix evenly, then drop 10 mL of 0.208 g / mL ammonium persulfate aqueous solution at 90°C, after the drop is completed, keep warm and stir to react for 30 minutes, then add 2.22 g of acrylamide, continue to keep warm and stir to react for 30 minutes, so that a block polymer layer of styrene and acrylamide can be formed on the surface of the acrylate prepolymer, so that the obtained reaction solution contains core-shell microspheres with the acrylate prepolymer as the inner shell and polystyrene-b-polyacrylamide as the outer shell; during the whole reaction process, the stirring rate is 280-290 r / min;

[0103] 3) The temperature was raised to 95°C, and an oxidation-reduction initiator system consisting of 0.16 g of tert-butyl hydroperoxide and 0.08 g of sodium formaldehyde sulfoxylate (for monomer elimination) was added. Ammonia water was then added dropwise to adjust the pH to 9. The mixture was stirred and reacted for 150 minutes (stirring rate was 280-290 r / min). The reaction was terminated to obtain a homogeneous emulsion-like reaction solution. The reaction solution was centrifuged and the separated precipitate was washed and filtered with ethanol and deionized water for 3-4 times. The filtered product was freeze-dried under vacuum to a constant weight to obtain powdered hollow polystyrene-b-polyacrylamide microspheres.

[0104] 2. Preparation of modified waterborne polyurea resin

[0105] a) nitrogen was introduced into a three-necked flask equipped with a constant pressure funnel, a mechanical stirrer, a constant temperature water bath and a spherical condenser for 15 minutes, so that the subsequent reaction system in the three-necked flask was under a nitrogen protection atmosphere, 7.0 g of isophorone diisocyanate (Mn = 250.24, 0.0280 mol) was first added to the flask, and then 21 g of polyetheramine D2000 (Mn = 1000, 0.0157 mol) was added dropwise to the flask at 40°C (the dropping rate was 7 seconds / drop). After the dropping was completed, the reaction was stirred and kept warm; then 0 .06 g of hollow polystyrene-b-polyacrylamide microspheres are dispersed in 2.1 g of acetone, and ultrasonically dispersed for 15 minutes to obtain a microsphere dispersion liquid, and the obtained microsphere dispersion liquid is added to a flask (the microsphere dispersion liquid can be prepared in advance, or it can be prepared on-site after adding diphenylmethane diisocyanate and polyetheramine. In this embodiment, the microsphere dispersion liquid is prepared on-site, and ultrasonically dispersed for 15 minutes to obtain the microsphere dispersion liquid, which is equivalent to stirring and reacting the mixture of diphenylmethane diisocyanate and polyetheramine for 15 minutes); then the obtained reaction system is kept warm and stirred for reaction for 3 hours;

[0106] b) heating to 80° C., adding 1.12 g of dimethylolbutyric acid as a hydrophilic chain extender, and stirring for 3 hours to obtain a polyurea prepolymer;

[0107] c) cooling to 70° C., adding 0.28 g of dimethylolpropane, and reacting with stirring for 1 hour to obtain a cross-linked product;

[0108] d) Cooling to 50°C, adding 0.765 g of hydrochloric acid, keeping the temperature for reaction for 45 minutes, then adding 50 mL of deionized water under high-speed shearing conditions for dispersion for 3 hours, and placing the obtained product in a vacuum drying oven for degassing (to remove residual organic solvent and bubbles) to obtain a modified waterborne polyurea resin with a solid content of 35%.

[0109] 3. Preparation of thermal insulation filler zinc titanate

[0110] 81.39 g of nano-titanium dioxide and 79.87 g of nano-zinc oxide powder (the molar ratio of nano-titanium dioxide: nano-zinc oxide is 1:1) are weighed, fully mixed in a ball mill and placed in a crucible, and the crucible is placed in a muffle furnace and calcined at 900° C. for 24 hours. The calcined product is crushed, ground, and sieved to obtain a product powder; 0.75 g of KH-550, 3.5 g of deionized water, and 31.5 g of ethanol are weighed and mixed to form a silane-modified liquid; 15 g of the product powder is added to the silane-modified liquid, and stirred at room temperature for 1 hour at a stirring speed of 300 r / min. The obtained product is filtered, washed, dried, ground, and sieved to obtain a thermal insulation filler zinc titanate.

[0111] 4. Preparation of zinc titanate reflective heat insulation modified waterborne polyurea coating

[0112] ① Add 20g deionized water, 0.6g wetting and dispersing agent BYK-180 and 0.3g defoaming agent BYK-019 into the reactor and stir to mix evenly;

[0113] ② Add 10g zinc titanate powder, 19g hollow glass microspheres and 1g silica nanoaerogel, and stir to mix evenly;

[0114] ③ Add 45g of modified waterborne polyurea resin and 0.05g of film-forming aid propylene glycol diacetate, and stir to mix evenly;

[0115] ④ Add 0.3g of anti-flash rust agent benzopyrimidine and 0.7g of leveling agent BYK-3455, and stir to mix evenly;

[0116] ⑤ Add 0.45g of pH adjuster AMP-95 and stir to mix evenly, so that the pH of the mixed liquid reaches 9;

[0117] ⑥ Add 0.9g of thickener polyacrylamide and stir to mix evenly to obtain the reflective heat-insulating water-based polyurea coating. This coating is called zinc titanate reflective heat-insulating modified water-based polyurea coating.

[0118] Figure 5 is a transmission electron micrograph of the hollow polystyrene-b-polyacrylamide microspheres prepared in this example; Figure 5 It can be seen that the microspheres prepared in this embodiment are hollow spherical. After testing, the size of the microspheres prepared in this embodiment is 100-110 nm. Figure 1 and Figure 5 It can be seen that during the preparation of microspheres, the polymerization stirring rate has a certain influence on the size of the final microspheres.

[0119] The heat insulation performance of the zinc titanate reflective heat insulation modified waterborne polyurea coating prepared in this embodiment was tested, and the test method is as follows:

[0120] 1) Thermal insulation temperature difference test: The surface of the stainless steel sheet was polished with 400-mesh sandpaper, and then ultrasonically treated with ethanol to remove impurities on the surface; the treated iron sheet surface was used as the wet film coating surface, and the coating was prepared using a wet film preparation device with a coating thickness of 250 μm on the wet film preparation device; finally, the coating was dried at room temperature for 1 hour and dried in a 90°C forced air oven for 3 hours to obtain a reflective insulating water-soluble polyurea coating, and the coating was subjected to a thermal insulation temperature difference test. The test results are shown in Table 1;

[0121] 2) Thermal conductivity test: The zinc titanate reflective thermal insulation modified waterborne polyurea coating was dripped into a cylindrical coating mold through a straw, dried at room temperature for 1 hour, and dried in a 90°C forced air oven for 3 hours to obtain a zinc titanate reflective thermal insulation modified waterborne polyurea circular coating. The coating was tested for thermal conductivity. The test results are shown in Table 2.

[0122] Comparative Example 1

[0123] The difference between this comparative example and Example 1 is that no reflective filler and heat-insulating filler are added during the preparation of the water-based polyurea coating, and the rest of the contents are the same as those described in Example 1. The specific preparation process is as follows:

[0124] 1. Preparation of hollow polystyrene-b-polyacrylamide microspheres

[0125] As described in Example 1.

[0126] 2. Preparation of modified waterborne polyurea resin

[0127] As described in Example 1.

[0128] 3. Preparation of waterborne polyurea coating

[0129] ① Add 20g of deionized water, 0.35g of wetting and dispersing agent EFKA-4570 and 0.25g of defoaming agent DC-62 into the reactor and stir to mix evenly;

[0130] ② Add 45g of modified waterborne polyurea resin and 0.05g of film-forming aid dodecanoate, and stir to mix evenly;

[0131] ③ Add 0.25g of anti-flash rust agent phthalimide and 0.5g of leveling agent BYK349, and stir to mix evenly;

[0132] ④ Add 0.4 g of ammonia water as pH adjuster, stir to mix evenly, and make the pH of the mixed liquid reach 9;

[0133] ⑤ Add 1g of thickener sodium carboxymethyl cellulose and stir to mix evenly to obtain a comparative water-based polyurea coating.

[0134] The waterborne polyurea coating prepared in this comparative example was tested for thermal insulation performance, and the test method is as follows:

[0135] 1) Thermal insulation temperature difference test: The surface of the stainless steel sheet was polished with 400-mesh sandpaper, and then ultrasonically treated with ethanol to remove impurities on the surface; the treated surface of the iron sheet was used as the wet film coating surface, and the coating was prepared using a wet film preparation device with a coating thickness of 250 μm on the wet film preparation device; finally, the coating was dried at room temperature for 1 hour and dried in a 90°C forced air oven for 3 hours to obtain a comparative waterborne polyurea coating, and the coating was subjected to a thermal insulation temperature difference test, and the test results are shown in Table 1;

[0136] 2) Thermal conductivity test: The comparative water-based polyurea coating was dripped into a cylindrical coating mold through a straw, dried at room temperature for 1 hour, and dried in a 90°C forced air oven for 3 hours to obtain a comparative water-based polyurea circular coating. The thermal conductivity of the coating was tested. The test results are shown in Table 2.

[0137] Comparative Example 2

[0138] The difference between this comparative example and Example 1 is that the reflective filler added in the preparation process of the water-based polyurea coating is rutile titanium dioxide, and the rest of the contents are the same as those described in Example 1. The specific preparation process is as follows:

[0139] 1. Preparation of hollow polystyrene-b-polyacrylamide microspheres

[0140] As described in Example 1.

[0141] 2. Preparation of modified waterborne polyurea resin

[0142] As described in Example 1.

[0143] 3. Preparation of waterborne polyurea coating

[0144] ① Add 20g of deionized water, 0.35g of wetting and dispersing agent EFKA-4570 and 0.25g of defoaming agent DC-62 into the reactor and stir to mix evenly;

[0145] ② Add 10g of rutile titanium dioxide, 19g of hollow glass microspheres and 1g of silica nano aerogel, and stir to mix evenly;

[0146] ③ Add 45g of modified waterborne polyurea resin and 0.05g of film-forming aid dodecanoate, and stir to mix evenly;

[0147] ④ Add 0.25g of anti-flash rust agent phthalimide and 0.5g of leveling agent BYK349, and stir to mix evenly;

[0148] ⑤ Add 0.4 g of ammonia water as a pH adjuster, stir to mix evenly, and make the pH of the resulting mixed liquid reach 9;

[0149] ⑥ Add 1g of thickener sodium carboxymethyl cellulose and stir to mix evenly to obtain a comparative water-based polyurea coating.

[0150] The waterborne polyurea coating prepared in this comparative example was tested for thermal insulation performance, and the test method is as follows:

[0151] 1) Thermal insulation temperature difference test: The surface of the stainless steel sheet was polished with 400-mesh sandpaper, and then ultrasonically treated with ethanol to remove impurities on the surface; the treated surface of the iron sheet was used as the wet film coating surface, and the coating was prepared using a wet film preparation device with a coating thickness of 250 μm on the wet film preparation device; finally, the coating was dried at room temperature for 1 hour and dried in a 90°C forced air oven for 3 hours to obtain a comparative waterborne polyurea coating, and the coating was subjected to a thermal insulation temperature difference test, and the test results are shown in Table 1;

[0152] 2) Thermal conductivity test: The comparative water-based polyurea was dripped into a cylindrical coating mold through a straw, dried at room temperature for 1 hour, and dried in a 90°C forced air oven for 3 hours to obtain a comparative water-based polyurea circular coating. The thermal conductivity of the coating was tested. The test results are shown in Table 2.

[0153] Comparative Example 3

[0154] The difference between this comparative example and Example 1 is that the water-based polyurea resin used in the preparation process of the water-based polyurea coating is a common water-based polyurea resin that has not been modified with hollow polystyrene-b-polyacrylamide microspheres. The rest of the contents are the same as those described in Example 1. The specific preparation process is as follows:

[0155] 1. Preparation of waterborne polyurea resin

[0156] a) nitrogen was introduced into a three-necked flask equipped with a constant pressure funnel, a mechanical stirrer, a constant temperature water bath and a spherical condenser for 20 minutes, so that the subsequent reaction system in the three-necked flask was under a nitrogen protection atmosphere, 7.0 g of hexamethylene diisocyanate (Mn=168.19, 0.0416 mol) was first added to the flask, and then 27.7 g of polyetheramine D2000 (Mn=2000, 0.0139 mol) was added dropwise to the flask at 45° C. (dropping rate was 7 seconds / drop), and after the dropping was completed, the reaction was stirred and kept warm for 2.5 hours;

[0157] b) heating to 85° C., adding 1.56 g of a hydrophilic chain extender, triethanolamine, and stirring for 2.5 hours to obtain a polyurea prepolymer;

[0158] c) Cooling to 45°C, adding 0.70 g of acetic acid, keeping the temperature for reaction for 30 minutes, then adding 45 mL of deionized water for dispersion for 2.5 hours under high-speed shearing conditions, and placing the obtained product in a vacuum drying oven for degassing (to remove residual organic solvent and bubbles) to obtain a water-based polyurea resin with a solid content of 35%.

[0159] 2. Preparation of thermal insulation filler zinc titanate

[0160] As described in Example 1.

[0161] 3. Preparation of waterborne polyurea coating

[0162] ① Add 20g of deionized water, 0.35g of wetting and dispersing agent EFKA-4570 and 0.25g of defoaming agent DC-62 into the reactor and stir to mix evenly;

[0163] ② Add 10g zinc titanate powder, 19g hollow glass microspheres and 1g silica nanoaerogel, and stir to mix evenly;

[0164] ③ Add 45g of water-based polyurea resin and 0.05g of film-forming aid 12-carbonate, and stir to mix evenly;

[0165] ④ Add 0.25g of anti-flash rust agent phthalimide and 0.5g of leveling agent BYK349, and stir to mix evenly;

[0166] ⑤ Add 0.4 g of ammonia water as a pH adjuster, stir to mix evenly, and make the pH of the resulting mixed liquid reach 9;

[0167] ⑥ Add 1g of thickener sodium carboxymethyl cellulose and stir to mix evenly to obtain a comparative water-based polyurea coating.

[0168] The waterborne polyurea coating prepared in this comparative example was tested for thermal insulation performance, and the test method is as follows:

[0169] 1) Thermal insulation temperature difference test: The surface of the stainless steel sheet was polished with 400-mesh sandpaper, and then ultrasonically treated with ethanol to remove impurities on the surface; the treated surface of the iron sheet was used as the wet film coating surface, and the coating was prepared using a wet film preparation device with a coating thickness of 250 μm on the wet film preparation device; finally, the coating was dried at room temperature for 1 hour and dried in a 90°C forced air oven for 3 hours to obtain a comparative waterborne polyurea coating, and the coating was subjected to a thermal insulation temperature difference test, and the test results are shown in Table 1;

[0170] 2) Thermal conductivity test: The comparative water-based polyurea coating was dripped into a cylindrical coating mold through a straw, dried at room temperature for 1 hour, and dried in a 90°C forced air oven for 3 hours to obtain a comparative water-based polyurea circular coating. The thermal conductivity of the coating was tested. The test results are shown in Table 2.

[0171] Comparative Example 4

[0172] The difference between this comparative example and Example 1 is that the water-based polyurea resin used in the preparation process of the water-based polyurea coating is a common water-based polyurea resin that has not been modified with hollow polystyrene-b-polyacrylamide microspheres, and the reflective filler added to the coating is rutile titanium dioxide. The specific preparation process is as follows:

[0173] 1. Preparation of waterborne polyurea resin

[0174] Same as described in Comparative Example 3.

[0175] 2. Preparation of waterborne polyurea coating

[0176] ① Add 20g of deionized water, 0.35g of wetting and dispersing agent EFKA-4570 and 0.25g of defoaming agent DC-62 into the reactor and stir to mix evenly;

[0177] ② Add 10g of rutile titanium dioxide, 19g of hollow glass microspheres and 1g of silica nano aerogel, and stir to mix evenly;

[0178] ③ Add 45g of water-based polyurea resin and 0.05g of film-forming aid 12-carbonate, and stir to mix evenly;

[0179] ④ Add 0.25g of anti-flash rust agent phthalimide and 0.5g of leveling agent BYK349, and stir to mix evenly;

[0180] ⑤ Add 0.4 g of ammonia water as a pH adjuster, stir to mix evenly, and make the pH of the resulting mixed liquid reach 9;

[0181] ⑥ Add 1g of thickener sodium carboxymethyl cellulose and stir to mix evenly to obtain a comparative water-based polyurea coating.

[0182] The waterborne polyurea coating prepared in this comparative example was tested for thermal insulation performance, and the test method is as follows:

[0183] 1) Thermal insulation temperature difference test: The surface of the stainless steel sheet was polished with 400-mesh sandpaper, and then ultrasonically treated with ethanol to remove impurities on the surface; the treated surface of the iron sheet was used as the wet film coating surface, and the coating was prepared using a wet film preparation device with a coating thickness of 250 μm on the wet film preparation device; finally, the coating was dried at room temperature for 1 hour and dried in a 90°C forced air oven for 3 hours to obtain a comparative waterborne polyurea coating, and the coating was subjected to a thermal insulation temperature difference test, and the test results are shown in Table 1;

[0184] 2) Thermal conductivity test: The comparative water-based polyurea coating was dripped into a cylindrical coating mold through a straw, dried at room temperature for 1 hour, and dried in a 90°C forced air oven for 3 hours to obtain a comparative water-based polyurea circular coating. The thermal conductivity of the coating was tested. The test results are shown in Table 2.

[0185] Comparative Example 5

[0186] This comparative example is about the preparation of hollow polystyrene-b-polyacrylamide microspheres, and the difference from Example 1 is only the stirring rate during the preparation process, which is as follows:

[0187] 1) First, 2.4g of α-methacrylic acid, 0.55g of hydroxyethyl methacrylate and 19g of methyl methacrylate were added into a flask, stirred to mix evenly, then 0.6g of sodium dodecylbenzene sulfonate and 100g of deionized water were added, stirred to mix evenly, and then 10mL of 0.021g / mL ammonium persulfate aqueous solution was dropped at 90°C. After the dropping was completed, the mixture was stirred and reacted for 80 minutes to obtain a suspension emulsion of acrylate prepolymer, referred to as core emulsion. During the whole reaction process, the stirring rate was 180 r / min.

[0188] 2) Weigh 25 g of the core emulsion prepared in step 1) and add it to a flask (the core emulsion here is equivalent to the seed in the seed emulsion polymerization method), then add 0.05 g of sodium dodecylbenzene sulfonate, 11.5 g of styrene and 14 g of deionized water, stir to mix evenly, then drop 10 mL of 0.208 g / mL ammonium persulfate aqueous solution at 90°C, after the drop is completed, keep warm and stir to react for 30 minutes, then add 2.22 g of acrylamide, continue to keep warm and stir to react for 30 minutes, so that a block polymer layer of styrene and acrylamide can be formed on the surface of the acrylate prepolymer, so that the obtained reaction solution contains core-shell microspheres with the acrylate prepolymer as the inner shell and polystyrene-b-polyacrylamide as the outer shell; during the whole reaction process, the stirring rate is 180 r / min;

[0189] 3) The temperature was raised to 95°C, and an oxidation-reduction initiation system consisting of 0.16 g of tert-butyl hydroperoxide and 0.08 g of sodium formaldehyde sulfoxylate (for monomer elimination) was added. Ammonia water was then added dropwise to adjust the pH to 9. The mixture was stirred and reacted for 150 minutes (stirring rate was 180 r / min). The reaction was terminated to obtain a heterogeneous reaction solution. The reaction solution was centrifuged and the separated precipitate was washed and filtered with ethanol and deionized water for 3 to 4 times. The filtered product was freeze-dried under vacuum to a constant weight to obtain powdered hollow polystyrene-b-polyacrylamide microspheres.

[0190] In this comparative example, after the reaction in step 3) is completed, the obtained reaction solution has agglomeration phenomenon and is a heterogeneous reaction solution. After separation, washing, filtration and freeze-drying, the obtained microsphere product has particles of different sizes and uneven morphology distribution, which is not suitable for the subsequent preparation of modified water-based polyurea resin. It can be seen that during the preparation of microspheres, the stirring rate also has a great influence on the morphology and size of the microspheres.

[0191] Table 1 Thermal insulation temperature difference test results of waterborne polyurea coatings prepared in Example 1 and Comparative Examples 1-4

[0192]

[0193] Table 2 Thermal conductivity test results of waterborne polyurea coatings prepared in Example 1 and Comparative Examples 1-4

[0194]

[0195] It can be seen from Table 1 and Table 2 that the method of the present invention (such as Example 1 and Example 2) can obtain a water-based polyurea coating with excellent thermal insulation performance, which has a large thermal insulation temperature difference and a low thermal conductivity coefficient; and, compared with the case where no reflective filler and thermal insulation filler are added (Comparative Example 1) or rutile titanium dioxide is used as the reflective filler (Comparative Example 2) or unmodified ordinary water-based polyurea resin is used (Comparative Example 3) or unmodified ordinary water-based polyurea resin and rutile titanium dioxide are used as the reflective filler (Comparative Example 4) under the same conditions, significant improvements are produced, which also shows that the technical solution of the present invention using the modified water-based polyurea resin grafted with hollow polystyrene-b-polyacrylamide microspheres as the base resin and zinc titanate as the reflective filler has a synergistic effect.

[0196] In addition, the thermal insulation performance of the waterborne polyurea coating prepared in Example 1 is better than that of the waterborne polyurea coating prepared in Example 2 (the thermal insulation temperature difference is relatively large and the thermal conductivity is relatively low), indicating that the size of the hollow polystyrene-b-polyacrylamide microspheres has a certain influence on the thermal insulation performance of the final waterborne polyurea coating. The waterborne polyurea coating prepared by using hollow polystyrene-b-polyacrylamide microspheres with a size of 150 to 160 nm prepared at a stirring rate of 220 to 230 r / min has better thermal insulation performance.

[0197] Finally, it should be pointed out that the above are only some preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above contents of the present invention all fall within the scope of protection of the present invention.

Claims

1. A reflective water-insulating polyurea coating, characterized in that: It has the following composition and ratio: Modified waterborne polyurea resin: 45-55 parts by mass; Deionized water: 15-20 parts by weight; Wetting and dispersing agent: 0.3-0.6 parts by mass; Defoaming agent: 0.05-0.35 parts by mass; Reflective filler: 10-15 parts by mass; Thermal insulation filler: 15-25 parts by mass; Film-forming aid: 0.05-2 parts by mass; Anti-flash rust agent: 0.1-0.4 parts by mass; Leveling agent: 0.5-2 parts by mass; pH adjuster: 0.01-0.05 parts by weight; Thickener: 0.4-1 parts by mass; The reflective filler is zinc titanate; The modified waterborne polyurea resin is obtained by grafting hollow polystyrene-b-polyacrylamide microspheres onto waterborne polyurea resin; the hollow polystyrene-b-polyacrylamide microspheres are firstly prepared by emulsion polymerization for preparing prepolymer, then prepared by seed emulsion polymerization for preparing core-shell microspheres with prepolymer as inner shell and polystyrene-b-polyacrylamide as outer shell, and finally obtained by removing the inner core of the core-shell microspheres by alkali swelling method.

2. The reflective water-insulating polyurea coating according to claim 1, characterized in that: The heat-insulating filler is any one of hollow glass microspheres, nano aerogels, and a mixture of hollow glass microspheres and nano aerogels.

3. The reflective water-insulating polyurea coating according to claim 1, characterized in that: The preparation of the modified waterborne polyurea resin comprises the following steps: a) under nitrogen protection, firstly add diisocyanate into the reactor, then add polyetheramine dropwise into the reactor at 40-50° C., after adding, heat-insulate and stir for 15-25 minutes; then disperse hollow polystyrene-b-polyacrylamide microspheres in an organic solvent to obtain a microsphere dispersion, and add the obtained microsphere dispersion into the reactor; then heat-insulate and stir the obtained reaction system for 2-3 hours; b) raising the temperature to 80-90° C., adding a hydrophilic chain extender, and stirring for 2-3 hours to obtain a polyurea prepolymer; c) cooling to 70-80° C., adding a crosslinking agent, and stirring for 1-1.5 hours to obtain a crosslinked product; d) cooling to 40-50° C., adding a neutralizing agent, keeping the temperature to react for 20-40 minutes, adding deionized water to disperse for 2-3 hours, and then placing the obtained product in a vacuum drying oven for degassing to obtain the modified waterborne polyurea resin.

4. The reflective water-insulating polyurea coating according to claim 3, characterized in that: In the preparation process of the modified waterborne polyurea resin, the mass ratio of hollow polystyrene-b-polyacrylamide microspheres: hydrophilic chain extender: cross-linking agent: neutralizer: (diisocyanate + polyetheramine) is (0.01-0.08): (1.1-1.2): (0.25-0.3): (0.7-0.8): (27.5-28.5); the molar ratio of diisocyanate: polyetheramine is (2-4): (0.9-1.1).

5. The reflective water-insulating polyurea coating according to claim 3, characterized in that: In step a), the diisocyanate is any one of isophorone diisocyanate, hexamethylene diisocyanate, and diphenylmethane diisocyanate; in step b), the hydrophilic chain extender is any one of dimethylolbutyric acid, N-methyldiethanolamine, and diethanolamine; in step c), the cross-linking agent is any one of trimethylolpropane, ethylene glycol, 1,4-butanediol, and dipropylene glycol; in step d), the neutralizing agent is any one of hydrochloric acid, acetic acid, chlorinated hydrocarbons, and triethylamine.

6. The reflective water-insulating polyurea coating according to claim 1, characterized in that: The preparation of the hollow polystyrene-b-polyacrylamide microspheres comprises the following steps: firstly preparing a suspension emulsion of an acrylate prepolymer by an emulsion polymerization method, then using the acrylate prepolymer as the core, forming a block polymer layer of styrene and acrylamide on the surface of the acrylate prepolymer by a seed emulsion polymerization method, thereby obtaining core-shell microspheres with the acrylate prepolymer as the inner shell and the polystyrene-b-polyacrylamide as the outer shell, and finally removing the inner core of the core-shell microspheres by an alkali swelling method using ammonia water, thereby obtaining the hollow polystyrene-b-polyacrylamide microspheres.

7. The reflective water-insulating polyurea coating according to claim 6, characterized in that: The preparation of the hollow polystyrene-b-polyacrylamide microspheres comprises the following steps: 1) First, α-methacrylic acid, hydroxyethyl methacrylate and methyl methacrylate are added into a reactor, stirred to mix evenly, then sodium dodecylbenzene sulfonate and deionized water are added, stirred to mix evenly, then an aqueous solution of ammonium persulfate is added dropwise at 85-90°C, and the mixture is stirred and reacted for 80-90 minutes to obtain a suspension emulsion of an acrylate prepolymer, referred to as a core emulsion; 2) Add a certain amount of the core emulsion prepared in step 1) into the reactor, add sodium dodecylbenzene sulfonate, styrene and deionized water, stir to mix evenly, then drop an aqueous solution of ammonium persulfate at 80-90° C., after the dropwise addition, stir and react for 30 minutes under heat preservation, then add acrylamide, and continue to stir and react for 30 minutes under heat preservation; 3) Raise the temperature to 90-95° C., add an oxidation-reduction initiation system consisting of an oxidant and a reductant, then drop ammonia water to adjust the pH to 9, then keep the mixture warm and stir for 150-160 minutes, and finally collect the solid product to obtain the hollow polystyrene-b-polyacrylamide microspheres.

8. The reflective water-insulating polyurea coating according to claim 1, characterized in that: The preparation of zinc titanate comprises the following steps: Equal amounts of nano-titanium dioxide and nano-zinc oxide powder are fully mixed in a ball mill and placed in a crucible, which is then placed in a muffle furnace for calcination. The calcined product is crushed, ground, and sieved, and the obtained product powder is added to a silane modification liquid for modification. The obtained product is filtered, washed, dried, ground, and sieved to obtain the zinc titanate thermal insulation filler.

9. The reflective water-insulating polyurea coating according to claim 8, characterized in that: The silane-modified liquid is composed of a silane coupling agent, water and ethanol, wherein the mass ratio of the silane coupling agent: water: ethanol is (0.5-0.1): (3.44-3.55): (30.96-31.95); and the mass ratio of the silane coupling agent: product powder is (4-5):

100.

10. A method for preparing the reflective water-insulating polyurea coating according to claim 1, characterized in that: The steps include: ① Add the proportion of deionized water, wetting dispersant and defoaming agent into the reactor and stir to mix them evenly; ② Add the proportion of reflective filler and heat-insulating filler, and stir to mix them evenly; ③ Add the modified waterborne polyurea resin and film-forming aid in a certain proportion, and stir to mix them evenly; ④Add the proportion of anti-flash rust agent and leveling agent, and stir to mix evenly; ⑤ Add a proportion of pH adjuster, stir to mix evenly, and make the pH of the resulting mixed liquid reach 9; ⑥ Add a proportion of thickener and stir to mix evenly to obtain the reflective water-insulating polyurea coating.

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