Composite hydrophobic ardealite water-based building thermal insulation coating and preparation method thereof

Abstract

The invention particularly relates to a composite hydrophobic ardealite water-based building thermal insulation coating and a preparation method thereof.The thermal insulation coating is a water-based emulsion and comprises polymer particles with a core layer and a shell layer structure, and the core layer structure comprises hydrophobic modified ardealite, a hydrophobic flame retardant and aerogel; and the shell structure is a silicone acrylic resin adhesive. The preparation method comprises the following steps: changing the size of powder by adopting a vertical mill jet milling process, carrying out hydrophobic modification on the surface of ardealite powder, compounding with a hydrophobic flame retardant and aerogel to obtain a hydrophobic spherical particulate kernel, mixing with a monomer of silicone acrylic resin, and polymerizing by adopting an emulsion method to obtain a spherical emulsion polymer coated with the silicone acrylic resin on the surface; the obtained thermal insulation coating has the characteristics of strong binding power, water resistance and high temperature resistance, and the thermal insulation, flame retardance, high temperature resistance and high humidity resistance of the coating are improved through integral combination; and the heat-insulating and fireproof material can be used for wall heat-insulating and fireproof engineering of high-humidity and large-temperature-difference scenes such as building outer walls, refrigeration houses, color steel tile roofs, mechanical equipment, chemical plants, underground pipe galleries and coastal buildings.

Description

Technical Field

[0001] The invention relates to a building thermal insulation material, in particular to a composite hydrophobic phosphogypsum water-based building thermal insulation coating and a preparation method thereof. Background Art

[0002] Phosphogypsum is the main by-product of phosphorus chemical industry, with huge annual discharge. Long-term storage leads to land occupation, heavy metal leachate pollution (such as F in phosphogypsum - , P2O5). Phosphogypsum, primarily composed of CaSO4·2H2O, becomes a Class A non-combustible material (GB 8624-2012) after conversion to β-hemihydrate gypsum. Its production energy consumption is only one-quarter that of cement, reducing carbon emissions by 60%. Alumina waste, containing ≥60% Al2O3, is used in architectural coatings. Compared to traditional insulation materials (such as polystyrene boards), which are flammable and have high carbon emissions, phosphogypsum has broad application prospects as a building insulation material.

[0003] However, the soluble P2O5 in phosphogypsum causes the coating to absorb moisture and soften. - The common method to improve the above defects is to wash the phosphogypsum with water to remove the corrosive fluorine-containing impurities, and then calcine it to produce stable β-hemihydrate gypsum, which increases flame retardancy and porosity by 50% to 60%, making it lightweight and porous.

[0004] Phosphogypsum-based materials have low compressive strength, typically less than 2 MPa, making them difficult to meet the strength requirements for exterior walls of high-rise buildings. They are typically combined with organic binders or cement to enhance their strength.

[0005] Invention CN114989656A discloses a thermal insulation slurry for building energy-saving coatings, which includes phosphogypsum, silica aerogel wet material and water. The thermal insulation slurry is mixed with film-forming substances such as acrylic acid and fillers to prepare a building energy-saving coating. However, the thermal insulation slurry and fillers have poor bonding performance with the film-forming substances and strong water absorption, resulting in poor storage stability and water resistance of the coating. In addition, acrylic paint itself will also be hot and brittle, and its application is limited in some environments, especially extreme environments, such as high temperature and high humidity, and high temperature difference scenarios. Therefore, there is an urgent need for a multifunctional composite material that is lightweight, heat-insulating, flame-retardant, and water-resistant. Summary of the Invention

[0006] In response to the above technical problems, the present invention proposes a phosphogypsum composite hydrophobic flame retardant thermal insulation material and a preparation method thereof, which can have multifunctional functions such as lightweight thermal insulation, flame retardancy and water resistance under extreme environments.

[0007] The present invention is achieved through the following solutions:

[0008] A composite hydrophobic phosphogypsum water-based building thermal insulation coating, comprising a water-based emulsion comprising polymer particles having a core layer and a shell layer structure dispersed in water, wherein the core layer structure comprises hydrophobically modified phosphogypsum, a hydrophobic flame retardant, and silica aerogel; the shell layer structure comprises a silicone-acrylic resin adhesive; and the mass ratio of the core layer to the shell layer of the polymer particles is 5-8:7-10.

[0009] Furthermore, the particle size of the polymer particles is 1-5 μm; the solid content of the aqueous emulsion is 40-60 wt%; and the mass ratio of the core layer hydrophobically modified phosphogypsum, the hydrophobic flame retardant and the silica aerogel is 3-5:1-2:1.

[0010] Furthermore, the preparation method of the hydrophobically modified phosphogypsum comprises the following steps:

[0011] 1) removing impurities from phosphogypsum to obtain pretreated phosphogypsum;

[0012] 2) The pretreated phosphogypsum is treated with a surface modifier and a solvent by vertical milling or jet milling, and then dried to obtain hydrophobically modified phosphogypsum; the surface modifier is a silane coupling agent, stearic acid or an organic carboxylate.

[0013] Furthermore, the pretreatment of the phosphogypsum in step 1) meets the second-level or above index of phosphogypsum in GB / T 23456-2018; and the D50 particle size of the hydrophobically modified phosphogypsum after the neutral mill / jet mill treatment in step 2) is 200-400 nm.

[0014] Furthermore, the amount of the surface modifier in step 2) is 1-6wt% of the pretreated phosphogypsum; the mass ratio of the surface modifier to the solvent is 1:6-8; the solvent is ethanol; the drying temperature is 60-80°C; and the silane coupling agent is KH550, KH570, KH560 or KH590.

[0015] Furthermore, the hydrophobic flame retardant is expanded graphite and / or silicone resin, and the volume-to-mass ratio of the expanded graphite is 300-400 mL / g; the thermal insulation coating also contains auxiliary materials, which are at least one of nano-titanium dioxide and an anti-aging agent; and the amount of the auxiliary materials added is 1-3 wt% of the silicone acrylic resin.

[0016] Furthermore, the preparation method of the composite hydrophobic phosphogypsum thermal insulation coating comprises the following steps:

[0017] (3) vertical milling / jet milling the hydrophobically modified phosphogypsum, the hydrophobic flame retardant, and the silica aerogel to obtain composite hydrophobically modified phosphogypsum particles;

[0018] (4) The product obtained in step (1) is uniformly mixed with the monomer of the silicone acrylic resin by ultrasonic dispersion, and slowly added dropwise into water containing a surfactant and a cosolvent under stirring conditions, and then an initiator is slowly added to carry out a polymerization reaction, and after the reaction, a thermal insulation coating containing core-shell structured phosphogypsum composite hydrophobic flame retardant polymer particles is obtained.

[0019] Furthermore, the particle size of the composite hydrophobically modified phosphogypsum particles after vertical mill / jet mill treatment in step (1) is 400nm-800nm; the monomers of the silicone-acrylic resin in step (2) are organic silicone monomers containing unsaturated double bonds and acrylic monomers; and the ultrasonic dispersion conditions are 30-50kHz, 10-30min.

[0020] Furthermore, the organic silicon monomer containing unsaturated double bonds in the step (2) is vinyl-terminated silicone oil SHYH-VI401 or KH-Vi series; the acrylic monomer is any one or more of methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, tert-butyl methacrylate, isobutyl methacrylate, isobornyl methacrylate or lauryl methacrylate; the emulsifier includes anionic emulsifier and nonionic emulsifier, the anionic emulsifier is sodium dodecyl sulfate or sodium dodecylbenzenesulfonate; the nonionic emulsifier is fatty alcohol polyoxyethylene ether or fatty alcohol ether phosphate; the initiator includes AIBN, BPO or ammonium persulfate; and the cosolvent is dipropylene glycol or propylene glycol propyl ether.

[0021] Furthermore, in step (2), the mass ratio of the silicone monomer containing an unsaturated double bond and the acrylic monomer is 1-3:6-8, the amounts of the initiator, emulsifier, and cosolvent are 0.5-1.5%, 5-10%, and 3-6% of the total mass of the monomers of the silicone acrylic resin, respectively, and the mass ratio of the anionic emulsifier to the nonionic emulsifier is 1-2:6-10; the polymerization reaction temperature is 50-60°C, the time is 1-3h, and the vinyl content is 0.5-1wt%.

[0022] The vertical jet mill combines a fluidized bed with a vertical classifier. Supersonic airflow impacts and pulverizes materials within the fluidized bed, reducing equipment wear and improving product purity. The vertical classifying wheel uses centrifugal force for precise classification, eliminating the need for compressed air seals and preventing large particle leakage, resulting in high classification efficiency. It can produce multiple particle size fractions simultaneously, with a narrow particle size distribution and a minimum particle size (D50) as low as 0.2 microns. This offers significant advantages over ball milling or grinding in powder processing.

[0023] Beneficial effects:

[0024] 1. The present invention uses a vertical jet mill process to change the powder size and modify the surface of the phosphogypsum powder. The phosphogypsum powder is then compounded with a hydrophobic flame retardant and aerogel to produce a hydrophobic spherical particle core. This core is then mixed with a silicone-acrylic resin monomer and polymerized using an emulsion method to produce a spherical emulsion polymer coated with silicone-acrylic resin. This appropriate process and novel design improve the dispersibility of the phosphogypsum and, after simultaneous hydrophobic modification, enhances its binding strength with an organic binder.

[0025] 2. The present invention adopts coating and emulsion polymerization technology to prepare a coating emulsion with a core-shell structure. The inner layer is a composite hydrophobically modified phosphogypsum to enhance the compatibility with the middle layer flame retardant and aerogel. The outermost layer is coated with a silicone acrylic resin adhesive. Through the synergistic strategy of hydrophobically modified phosphogypsum, hydrophobic flame retardant compounding and aerogel enhancement, a lightweight, heat-insulating, flame-retardant and water-resistant inner skeleton is designed. The outer layer adhesive is a high-temperature and aging-resistant silicone acrylic resin, which is suitable for construction and industrial insulation in extreme environments (such as high humidity and high temperature difference scenes); the inner layer and the outer layer are combined to synergistically improve the thermal insulation, flame retardancy and high-temperature and high-humidity resistance of the coating; it can be used for wall insulation and fire protection projects in high-humidity and large temperature difference scenes such as building exterior walls, cold storage, color steel tile roofs, mechanical equipment, chemical plant rooms, underground pipe corridors, coastal buildings, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 The present invention provides a flow chart for preparing a composite hydrophobic phosphogypsum water-based building thermal insulation coating.

[0028] Figure 2 This is a schematic diagram of the process of preparing a composite hydrophobic phosphogypsum water-based building insulation coating by emulsion polymerization of the present invention.

[0029] Figure 3 This is a particle size diagram of the water-based thermal insulation coating obtained in Example 1. DETAILED DESCRIPTION

[0030] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without creative work are within the scope of protection of the present invention.

[0031] Example 1

[0032] This embodiment prepares a method for preparing a composite hydrophobic phosphogypsum water-based building insulation coating, such as Figure 1 As shown, the following steps are included:

[0033] (1) washing phosphogypsum lime milk, washing with water, and then drying to obtain pretreated phosphogypsum; the specific method can be found in patent CN103708750A and will not be described in detail here. The obtained pretreated phosphogypsum meets the GB / T 23456-2018 phosphogypsum level 2 or above indicators, calcium sulfate dihydrate dry basis ≥80%, P2O5 ≤0.3%, water-soluble fluoride ion ≤0.2%, water-soluble sodium oxide ≤0.1%, chloride ion ≤0.04%, and can be used as building material gypsum;

[0034] (2) 20 g of pretreated phosphogypsum was treated with a silane coupling agent KH550 and a solvent by vertical milling / jet milling, with the volume ratio of the silane coupling agent to ethanol being 1:7; and dried at 70° C. to obtain hydrophobically modified phosphogypsum; the amount of the silane coupling agent was 4 wt % of the pretreated phosphogypsum; and the D50 particle size of the obtained hydrophobically modified phosphogypsum was 300 nm.

[0035] (3) mixing the hydrophobically modified phosphogypsum with the hydrophobic flame retardant expanded graphite and silica aerogel in a mass ratio of 4:1.5:1, then jet milling, adding 1 wt% of the material to be ground into a silane coupling agent; obtaining composite hydrophobically modified phosphogypsum particles with a particle size of 600 nm;

[0036] (4) Schematic diagram of the process of preparing composite hydrophobic phosphogypsum water-based building insulation coating through emulsion polymerization Figure 2 As shown; the product obtained in step (3) is uniformly mixed with the monomer of silicone acrylic resin by ultrasonic dispersion at a mass ratio of 7:8, and the ultrasonic dispersion conditions are 40kHz, 20min; under the stirring condition of 1000rpm, it is slowly added dropwise to water containing surfactant and cosolvent, and an initiator is slowly added to carry out polymerization reaction, and after the reaction, a water-based emulsion thermal insulation coating of a core-shell structured phosphogypsum composite hydrophobic flame retardant is obtained, the solid content of the water-based emulsion is 55wt%, the particle size of the polymer particles is 3μm, and the particle size distribution is as shown Figure 3 shown.

[0037] The monomer of the silicone-acrylic resin is a mixture of vinyl-terminated silicone oil SHYH-VI401, methyl methacrylate, and lauryl methacrylate in a mass ratio of 3:2:3; the vinyl content of the vinyl-terminated silicone oil is 0.8wt%; the acrylic monomer emulsifier is a mixture of sodium lauryl sulfate and fatty alcohol ether phosphate in a mass ratio of 1.5:7; the initiator includes potassium persulfate; and the cosolvent is dipropylene glycol.

[0038] The amounts of the initiator, emulsifier and cosolvent are 0.5-1.5%, 5-10% and 3-6% of the total mass of the silicone acrylic resin monomer, respectively. The polymerization temperature is 55° C. and the time is 2 hours. A water-based thermal insulation coating is obtained, in which the particle size of the polymer microparticle emulsion is 3 μm; and the solid content of the water-based emulsion is 55 wt%.

[0039] After the water-based thermal insulation coating obtained in this example was cured, the performance was tested:

[0040] The water absorption rate of the coating after immersion for 72 hours is 2.8% (test standard ASTM D1653);

[0041] Self-extinguishing time in vertical combustion test ≤3s, no dripping (UL94 standard);

[0042] Thermal conductivity is 0.043W / (m·K) (test standard ASTM C518);

[0043] Freeze-thaw resistance of architectural coatings: No powdering, cracking or peeling after 50 cycles at -20℃ to 50℃ (JG / T25-1999).

[0044] Example 2

[0045] This embodiment prepares a method for preparing a composite hydrophobic phosphogypsum water-based building insulation coating, comprising the following steps:

[0046] (1) washing phosphogypsum lime milk, washing with water, and then drying to obtain pretreated phosphogypsum; the specific method can be found in patent CN103708750A and will not be described in detail here. The obtained pretreated phosphogypsum meets the GB / T 23456-2018 phosphogypsum level 2 or above indicators, calcium sulfate dihydrate dry basis ≥80%, P2O5 ≤0.3%, water-soluble fluoride ion ≤0.2%, water-soluble sodium oxide ≤0.1%, chloride ion ≤0.04%, and can be used as building material gypsum;

[0047] (2) 20 g of pretreated phosphogypsum and an ethanol solution of silane coupling agent KH560 were vertically milled / jet milled together, with the volume ratio of silane coupling agent to ethanol being 1:6; and dried at 60° C. to obtain hydrophobically modified phosphogypsum; the amount of silane coupling agent used was 1-6 wt % of the pretreated phosphogypsum; and the obtained hydrophobically modified phosphogypsum had a D50 particle size of 200 nm.

[0048] (3) mixing the hydrophobically modified phosphogypsum with the hydrophobic flame retardant expanded graphite and the thermal insulation material silica aerogel in a mass ratio of 3:1:1, vertically grinding and then jet milling, adding a silane coupling agent of 0.5-2% of the material to be ground; obtaining composite hydrophobically modified phosphogypsum particles with a particle size of 500 nm;

[0049] (4) The product obtained in step (3) is uniformly mixed with the monomer of silicone acrylic resin by ultrasonic dispersion at a mass ratio of 5:7, and the ultrasonic dispersion conditions are 30 kHz and 30 min; under stirring conditions of 1200 rpm, it is slowly added dropwise to water containing a surfactant and a cosolvent, and an initiator is slowly added to carry out a polymerization reaction at a temperature of 50°C and a time of 3 hours; after the reaction, a core-shell structure composite hydrophobic phosphogypsum water-based building insulation coating is obtained, the solid content of the aqueous emulsion is 50wt%, and the particle size of the polymer particles is 3μm.

[0050] The monomers of the silicone acrylic resin are vinyl-terminated silicone oil SHYH-VI401, a mixture of methyl methacrylate and ethyl methacrylate in a mass ratio of 2:3:3; the vinyl content of the vinyl silicone oil SHYH-VI401 is 0.5wt%, and the emulsifier is sodium lauryl sulfate and fatty alcohol polyoxyethylene ether in a mass ratio of 1:6; the initiator includes ammonium persulfate; the cosolvent is dipropylene glycol; the amounts of the initiator, emulsifier and cosolvent are 1%, 5% and 3% of the total mass of the monomers of the silicone acrylic resin, respectively.

[0051] Example 3

[0052] This embodiment prepares a method for preparing a composite hydrophobic phosphogypsum water-based building insulation coating, comprising the following steps:

[0053] (1) acid-washing and water-washing the phosphogypsum, and then drying and ball-milling the phosphogypsum to obtain pretreated phosphogypsum; the pretreated phosphogypsum meets the second-level or above index of GB / T23456-2018 phosphogypsum;

[0054] (2) 20 g of pretreated phosphogypsum and an ethanol solution of silane coupling agent KH590 were vertically milled / jet milled together, with the volume ratio of silane coupling agent to ethanol being 1:6; and dried at 60° C. to obtain hydrophobically modified phosphogypsum; the amount of silane coupling agent used was 1-6 wt % of the pretreated phosphogypsum; and the obtained hydrophobically modified phosphogypsum had a D50 particle size of 400 nm.

[0055] (3) mixing the hydrophobically modified phosphogypsum with the hydrophobic flame retardant silicone resin and the thermal insulation material silica aerogel in a mass ratio of 5:2:1, vertically grinding and then jet milling, adding a silane coupling agent of 0.5% of the material to be ground; obtaining composite hydrophobically modified phosphogypsum particles with a particle size of 800 nm;

[0056] (4) The product obtained in step (3) is uniformly mixed with the monomer of silicone acrylic resin by ultrasonic dispersion at a mass ratio of 8:10, and the ultrasonic dispersion conditions are 50kHz and 10min; under the stirring condition of 700r / min, it is slowly added dropwise to water containing surfactant and cosolvent, and an initiator is slowly added to carry out polymerization reaction at a temperature of 50°C and a time of 3h. After the reaction, a core-shell structure composite hydrophobic phosphogypsum water-based building insulation coating is obtained; the solid content of the aqueous emulsion is 45wt%, and the particle size of the polymer particles is 5μm.

[0057] The monomers of the silicone-acrylic resin are a mixture of vinyl-terminated silicone oil KH-Vi series, butyl methacrylate, and 2-ethylhexyl methacrylate in a mass ratio of 3:4:4; the vinyl content of the vinyl-terminated silicone oil KH-Vi series is 1wt%, and the emulsifier is a mixture of sodium dodecylbenzenesulfonate and fatty alcohol ether phosphate in a mass ratio of 1:10; the initiator includes AIBN and BPO; the cosolvent is propylene glycol propyl ether; the amounts of the initiator, emulsifier, and cosolvent are 1.5%, 10%, and 6% of the total mass of the monomers of the silicone-acrylic resin, respectively.

[0058] Example 4

[0059] This embodiment prepares a method for preparing a composite hydrophobic phosphogypsum water-based building insulation coating, comprising the following steps:

[0060] (1) acid-washing and water-washing the phosphogypsum, and then drying and ball-milling the phosphogypsum to obtain pretreated phosphogypsum; the pretreated phosphogypsum meets the second-level or above index of GB / T23456-2018 phosphogypsum;

[0061] (2) 20 g of pretreated phosphogypsum and an ethanol solution of silane coupling agent KH590 were vertically milled / jet milled together, with the volume ratio of silane coupling agent to ethanol being 1:8; and dried at 60° C. to obtain hydrophobically modified phosphogypsum; the amount of silane coupling agent used was 1-6 wt % of the pretreated phosphogypsum; and the obtained hydrophobically modified phosphogypsum had a D50 particle size of 200 nm.

[0062] (3) mixing the hydrophobically modified phosphogypsum with the hydrophobic flame retardant expanded graphite and the thermal insulation material silica aerogel in a mass ratio of 4:2:1, vertically grinding and then jet milling, adding a silane coupling agent of 2% of the material to be ground; obtaining composite hydrophobically modified phosphogypsum particles with a particle size of 400 nm;

[0063] (4) The product obtained in step (3) is uniformly mixed with the monomer of silicone acrylic resin by ultrasonic dispersion at a mass ratio of 7:9, and the ultrasonic dispersion conditions are 50kHz, 10-min; under the stirring condition of 900r / min, it is slowly added dropwise to water containing surfactant and cosolvent, and an initiator is slowly added to carry out polymerization reaction at a temperature of 50-60°C and a time of 1-3h; after the reaction, a core-shell structure composite hydrophobic phosphogypsum water-based building insulation coating is obtained, the solid content of the aqueous emulsion is 60wt%, and the particle size of the polymer particles is 1μm.

[0064] The monomers of the silicone-acrylic resin are a mixture of vinyl-terminated silicone oil SHYH-VI401 and tert-butyl methacrylate and isobutyl methacrylate in a mass ratio of 2:3:4; the vinyl content of the vinyl-terminated silicone oil SHYH-VI401 is 0.1-1wt%; the emulsifier is a mixture of sodium lauryl sulfate and fatty alcohol polyoxyethylene ether in a ratio of 2:7; the initiator includes AIBN; the cosolvent is dipropylene glycol; the amounts of the initiator, emulsifier and cosolvent are 1%, 5% and 3% of the total mass of the monomers of the silicone-acrylic resin, respectively.

[0065] Example 5

[0066] This embodiment prepares a method for preparing a composite hydrophobic phosphogypsum water-based building insulation coating, comprising the following steps:

[0067] (1) acid-washing and water-washing the phosphogypsum, and then drying and ball-milling the phosphogypsum to obtain pretreated phosphogypsum; the pretreated phosphogypsum meets the second-level or above index of GB / T23456-2018 phosphogypsum;

[0068] (2) 20 g of pretreated phosphogypsum and an ethanol solution of stearic acid were vertically milled / jet milled together, with the volume ratio of stearic acid to ethanol being 1:6-8; and dried at 60° C. to obtain hydrophobically modified phosphogypsum; the amount of stearic acid used was 1-6 wt % of the pretreated phosphogypsum; and the obtained hydrophobically modified phosphogypsum had a D50 particle size of 200-400 nm.

[0069] (3) mixing the hydrophobically modified phosphogypsum with the hydrophobic flame retardant expanded graphite and the thermal insulation material silica aerogel in a mass ratio of 3:1:1, vertically grinding and then jet milling, adding a silane coupling agent of 0.5-2% of the material to be ground; obtaining composite hydrophobically modified phosphogypsum particles with a particle size of 800 nm;

[0070] (4) The product obtained in step (3) is uniformly mixed with the monomer of the silicone acrylic resin by ultrasonic dispersion at a mass ratio of 5:7, and the ultrasonic dispersion conditions are 30 kHz and 30 min; under the stirring condition of 800 rpm, it is slowly added dropwise to water containing a surfactant, a cosolvent and an auxiliary material titanium dioxide, and an initiator is slowly added to carry out a polymerization reaction, and the polymerization reaction temperature is 55°C and the time is 2 hours; after the reaction, composite hydrophobic phosphogypsum water-based building insulation coating latex particles with a core-shell structure are obtained, the solid content of the aqueous emulsion is 40wt%, and the particle size of the polymer particles is 5μm;

[0071] The monomers of the silicone acrylic resin are vinyl-terminated silicone oil SHYH-VI401, acrylic monomers isobornyl methacrylate and lauryl methacrylate in a mass ratio of 1:3:3; the vinyl-terminated silicone oil SHYH-VI401 has a vinyl content of 0.5wt%; the emulsifier is a mixture of sodium lauryl sulfate and fatty alcohol ether phosphate in a mass ratio of 1:6; the initiator is ammonium persulfate; the cosolvent is propylene glycol propyl ether; the amounts of the initiator, emulsifier, cosolvent and auxiliary materials are 1%, 5%, 3% and 2% of the total mass of the monomers of the silicone acrylic resin, respectively.

[0072] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A composite hydrophobic phosphogypsum water-based building thermal insulation coating, characterized in that: The water-based building insulation coating is a water-based emulsion, which is a polymer particle with a core layer and a shell layer structure dispersed in water. The core layer structure includes hydrophobically modified phosphogypsum, a hydrophobic flame retardant and silica aerogel; the shell layer structure is a silicone acrylic resin adhesive; the mass ratio of the core layer to the shell layer of the polymer particle is 5-8:7-10.

2. The composite hydrophobic phosphogypsum water-based building thermal insulation coating according to claim 1, characterized in that: The particle size of the polymer particles is 1-5 μm; the solid content of the aqueous emulsion is 40-60 wt%; and the mass ratio of the core layer hydrophobically modified phosphogypsum, the hydrophobic flame retardant and the silica aerogel is 3-5:1-2:

1.

3. The composite hydrophobic phosphogypsum water-based building thermal insulation coating according to claim 1, characterized in that: The preparation method of the hydrophobically modified phosphogypsum comprises the following steps: 1) removing impurities from phosphogypsum to obtain pretreated phosphogypsum; 2) treating the pretreated phosphogypsum, a surface modifier and a solvent together with a vertical mill / jet mill and drying to obtain hydrophobically modified phosphogypsum; the surface modifier is a silane coupling agent, stearic acid or an organic carboxylate.

4. The composite hydrophobic phosphogypsum water-based building thermal insulation coating according to claim 3, characterized in that: In the step 1), the pretreatment of the phosphogypsum meets the GB / T 23456-2018 phosphogypsum level 2 or above index; and in the step 2), the D50 particle size of the hydrophobically modified phosphogypsum after the neutral mill / jet mill treatment is 200-400 nm.

5. The composite hydrophobic phosphogypsum water-based building thermal insulation coating according to claim 3, characterized in that: The amount of the surface modifier in step 2) is 1-6wt% of the pretreated phosphogypsum; the mass ratio of the surface modifier to the solvent is 1:6-8; the solvent is ethanol; the drying temperature is 60-80°C; and the silane coupling agent is KH550, KH570, KH560 or KH590.

6. The composite hydrophobic phosphogypsum water-based building thermal insulation coating according to any one of claims 1 to 5, characterized in that: The hydrophobic flame retardant is expanded graphite and / or silicone resin; the volume-to-mass ratio of the expanded graphite is 300-400 mL / g; the thermal insulation coating further contains auxiliary materials, which are at least one of nano-titanium dioxide and an anti-aging agent; the added amount of the auxiliary materials is 1-3 wt% of the silicone acrylic resin.

7. The method for preparing the composite hydrophobic phosphogypsum water-based building thermal insulation coating according to any one of claims 1 to 6, characterized in that: The steps include: (1) grinding the hydrophobically modified phosphogypsum, the hydrophobic flame retardant and the silica aerogel into a vertical mill / jet mill to obtain composite hydrophobically modified phosphogypsum particles; (2) The product obtained in step (1) is uniformly mixed with the monomer of the silicone acrylic resin by ultrasonic dispersion, and slowly added dropwise into water containing a surfactant and a cosolvent under stirring conditions, and then an initiator is slowly added to carry out a polymerization reaction, and after the reaction, a thermal insulation coating containing core-shell structured phosphogypsum composite hydrophobic flame retardant polymer particles is obtained.

8. The method for preparing the composite hydrophobic phosphogypsum water-based building thermal insulation coating according to claim 7, wherein: The particle size of the composite hydrophobically modified phosphogypsum particles after vertical mill / jet mill treatment in step (1) is 400nm-800nm; the monomers of the silicone-acrylic resin in step (2) are organic silicone monomers containing unsaturated double bonds and acrylic monomers; and the ultrasonic dispersion conditions are 30-50kHz, 10-30min.

9. The method for preparing the composite hydrophobic phosphogypsum water-based building thermal insulation coating according to claim 7, wherein: In the step (2), the organosilicon monomer containing unsaturated double bonds is vinyl-terminated silicone oil SHYH-VI401 or KH-Vi series; the acrylic monomer is any one or more of methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, tert-butyl methacrylate, isobutyl methacrylate, isobornyl methacrylate or lauryl methacrylate; the emulsifier includes anionic emulsifier and nonionic emulsifier, the anionic emulsifier is sodium dodecyl sulfate or sodium dodecylbenzenesulfonate; the nonionic emulsifier is fatty alcohol polyoxyethylene ether or fatty alcohol ether phosphate; the initiator includes AIBN, BPO or ammonium persulfate; and the cosolvent is dipropylene glycol or propylene glycol propyl ether.

10. The method for preparing the composite hydrophobic phosphogypsum water-based building thermal insulation coating according to claim 7, characterized in that: In step (2), the mass ratio of the silicone monomer containing an unsaturated double bond and the acrylic monomer is 1-3:6-8, the amounts of the initiator, emulsifier, and cosolvent are 0.5-1.5%, 5-10%, and 3-6% of the total mass of the silicone acrylic resin monomer, respectively, and the mass ratio of the anionic emulsifier to the nonionic emulsifier is 1-2:6-10; the polymerization reaction temperature is 50-60° C., the reaction time is 1-3 h, and the vinyl content is 0.5-1wt%.

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