A kind of PVDF fluorocarbon paint based on nanoparticle modification and preparation method thereof

Abstract

The invention provides a PVDF fluorocarbon paint based on nanoparticle modification and a preparation method thereof, comprising the following raw materials in parts by weight: 45-50 parts of aqueous PVDF fluorocarbon emulsion, 20-27 parts of aqueous epoxy resin emulsion, 10-15 parts of acrylic emulsion, 10-14 parts of inorganic pigment, 12-17 parts of modified nanoparticles, 35-40 parts of film-forming cosolvent, 1-2 parts of defoamer, 1-3 parts of dispersant, 6-10 parts of silica hyperbranched curing agent and 30-35 parts of water. The PVDF fluorocarbon paint prepared by the invention has excellent comprehensive performance and is suitable for use as coil coating.

Description

Technical Field

[0001] The invention belongs to the technical field of coatings, and in particular relates to a PVDF fluorocarbon paint based on nanoparticle modification and a preparation method thereof. Background Art

[0002] PVDF (polyvinylidene fluoride) fluorocarbon paint is a high-performance paint that uses PVDF resin as the main film-forming substance. This paint has excellent weather resistance, corrosion resistance and color stability, and can maintain its original appearance and function under extreme weather conditions. Therefore, it is widely used in the construction field that requires long-term protection and aesthetic effects.

[0003] Although PVDF fluorocarbon paint performs well in many applications due to its excellent weather resistance, chemical resistance and color stability, it also has some potential drawbacks when used as a coil coating: (1) Flexibility limitations: PVDF coatings may become brittle at low temperatures, affecting their flexibility and impact resistance, which is a challenge for coils that require good bending properties. (2) Adhesion issues: Although PVDF coatings have good adhesion to some substrates, it may not adhere well to some metal or plastic substrates with improper surface treatment. (3) Thermal stability: Although PVDF has good thermal stability under normal conditions, it may decompose and release harmful gases such as hydrogen fluoride under extremely high temperatures, such as building fires, which is a consideration in terms of safety. (4) Environmental impact: Although PVDF itself is relatively environmentally friendly, its production and waste disposal processes may still impose a certain burden on the environment. (5) Chemical resistance limitations: Although PVDF has excellent chemical resistance, its performance may be limited in certain specific chemical environments, such as strong alkalis or specific solvents.

[0004] In view of the potential defects of PVDF fluorocarbon paint in coil coating applications, the existing technology has adopted a variety of strategies to improve or overcome these problems: (1) Enhanced flexibility: By adjusting the coating formula and adding acrylic emulsion to PVDF fluorocarbon emulsion, the low-temperature flexibility and impact resistance of PVDF coating can be improved. (2) Improved adhesion: Develop special primers or pretreatment technologies to enhance the adhesion between PVDF coating and different substrates to ensure the stability and durability of the coating. (3) Improved thermal stability: Although the thermal stability of PVDF is already very high, its safety performance under extreme high temperatures can be further improved by optimizing the formula and adding flame retardants. (4) Enhanced chemical resistance: By modifying the PVDF resin, the stability of the coating in a specific chemical environment is improved. Generally, coil coatings have a high demand for aging resistance, but the aging resistance of the PVDF fluorocarbon paint prepared by the above method is not ideal, and its properties such as moisture and heat resistance cannot meet the needs of the existing market.

[0005] Therefore, there is an urgent need for a PVDF fluorocarbon paint based on nanoparticle modification and a preparation method thereof. Summary of the invention

[0006] The purpose of the present invention is to provide a PVDF fluorocarbon paint based on nanoparticle modification and a preparation method thereof.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] A nanoparticle-modified PVDF fluorocarbon paint comprises the following raw materials in parts by weight: 45-50 parts of water-based PVDF fluorocarbon emulsion, 20-27 parts of water-based epoxy resin emulsion, 10-15 parts of acrylic emulsion, 10-14 parts of inorganic pigment, 12-17 parts of modified nanoparticles, 35-40 parts of film-forming cosolvent, 1-2 parts of defoamer, 1-3 parts of dispersant, 6-10 parts of silica hyperbranched curing agent and 30-35 parts of water;

[0009] The preparation method of the modified nanoparticles is:

[0010] (1) mixing carbon nanotubes, nano calcium carbonate and DK2 nano montmorillonite in a mass ratio of 1:0.2-0.5:1.5-1.8 to obtain mixed nanoparticles;

[0011] (2) Evenly stir an ethanol aqueous solution, mixed nanoparticles and KH-560 in a mass ratio of 8-10:1:0.2-0.3, raise the temperature to 60-65°C and react for 100-150 minutes, filter and dry the filter cake to obtain modified nanoparticles.

[0012] Furthermore, the fluorine content in the water-based PVDF fluorocarbon emulsion is ≥15%, and the solid content is 45±2%. Qingdao Hongfeng Fluorosilicone Technology Co., Ltd., model hfs-f-3301.

[0013] Furthermore, the solid content of the acrylic emulsion is 45±1%, and the glass transition temperature is 20° C. Anhui Zhongen Chemical Co., Ltd., model: PA-511.

[0014] Furthermore, the epoxy equivalent of the waterborne epoxy resin emulsion is 500-600 g / eq, and the viscosity at 25° C. is 1000-6000 mPa·s. Brand: American Hexam Momentive, Model: Epikote6520-WH-53A.

[0015] In the prior art, acrylic emulsion is added to water-based PVDF fluorocarbon emulsion to improve the aging resistance of PVDF fluorocarbon paint, but the effect is not ideal. The present invention reduces the amount of traditional acrylic emulsion added, and adds water-based epoxy resin emulsion at the same time. By compounding water-based PVDF fluorocarbon emulsion, water-based epoxy resin emulsion and acrylic emulsion, the aging resistance of PVDF fluorocarbon paint is significantly improved. Water-based epoxy resin emulsion undergoes cross-linking reaction during the curing process to form a three-dimensional network structure, and forms a more complex cross-linking network with water-based PVDF fluorocarbon emulsion and acrylic emulsion, thereby improving the aging resistance of PVDF fluorocarbon paint. When using water-based PVDF fluorocarbon emulsion, water-based epoxy resin emulsion and acrylic emulsion with specific parameters, T-bend performance is improved and the flexibility of the coating is better. However, after only adding water-based epoxy resin emulsion, the solvent wiping resistance and moisture and heat resistance of PVDF fluorocarbon paint are not ideal.

[0016] The present invention attempts to improve the moisture and heat resistance of PVDF fluorocarbon paint by adding nano materials, but it is found in experiments that agglomeration is easy to occur, and the effect is not ideal. The present invention improves the moisture and heat resistance of PVDF fluorocarbon paint by modifying three kinds of nano particles to obtain modified nano particles and adding them into the system. By adding modified fillers, the interface compatibility can be improved, the curing and cross-linking of PVDF fluorocarbon paint can be promoted, and the porosity inside the PVDF fluorocarbon paint can be reduced.

[0017] Furthermore, the preparation method of the silica hyperbranched curing agent is:

[0018] S1: Add 1 part by mass of sodium silicate aqueous solution and 3-5 parts by mass of sulfuric acid solution to 10-15 parts by mass of 50-55°C water, keep warm and react for 6-10 hours, then adjust the pH to 10-11 with sodium hydroxide, add 2-4 parts by mass of calcium chloride, heat to 60-70°C and react for 25-30 hours, filter, wash, dry and crush after the reaction to obtain calcium ion exchange silica pigment;

[0019] S2: Mix 1 part by mass of calcium ion exchange silica pigment, 0.1-0.2 parts by mass of coupling agent KH550 and 6-8 parts by mass of water, stir at 100° C. for 10-15 hours, filter, wash, dry and crush to obtain a silica hyperbranched curing agent.

[0020] The present invention improves the solvent wiping resistance of PVDF fluorocarbon paint by adding a silicon dioxide hyperbranched curing agent. The present invention forms a spherical hyperbranched structure with ultra-high functionality by grafting a large number of amino functional groups and allyl functional groups on the surface of silicon dioxide particles. The amino functional groups can react with epoxy groups in epoxy resin to form stable amino-ether bonds. The amino functional groups can form hydrogen bonds with fluorocarbon chains in PVDF or carboxyl groups in acrylic chains to enhance the interaction between particles and polymer matrices. The silicon dioxide particles with hyperbranched structures can serve as bridges between polymer matrices, and the solvent wiping resistance of PVDF fluorocarbon paint is improved through the interaction between functional groups and polymer chain segments. Under this condition, the impact resistance of PVDF fluorocarbon paint is also improved.

[0021] Furthermore, the mass percentage of sodium silicate in the sodium silicate aqueous solution is 40-55%.

[0022] Furthermore, H 2 SO 4 The mass percentage is 50-60%.

[0023] Furthermore, the mass concentration of the ethanol aqueous solution is 60-70%.

[0024] The diameter of carbon nanotubes is 1-2nm, the length is 10-30μm, and the average specific surface area is 1380m 2 / g. Purchased from Xianfeng Nano.

[0025] The particle size of nano calcium carbonate is 0.01-0.1μm and the specific surface area is 20-80m 2 / g.

[0026] The DK2 nano-montmorillonite was purchased from Zhejiang Fenghong New Materials Co., Ltd.

[0027] Furthermore, the film-forming co-solvent is a mixture of propylene glycol methyl ether, ethylene glycol butyl ether and dipropylene glycol methyl ether in a mass ratio of 1:1.3-1.6:0.5-0.8.

[0028] Furthermore, the inorganic pigment is rutile titanium dioxide.

[0029] Furthermore, the defoaming agent is BYK-024.

[0030] Furthermore, the dispersant is BYK-190.

[0031] The present invention also provides a method for preparing a PVDF fluorocarbon paint modified by nanoparticles, the method comprising the following steps: adding an inorganic pigment, a defoamer, and a dispersant to water in sequence, and dispersing the mixture evenly at high speed; and continuously adding an aqueous PVDF fluorocarbon emulsion, an aqueous epoxy resin emulsion, an acrylic emulsion, an inorganic pigment, modified nanoparticles, a film-forming cosolvent, and a silica hyperbranched curing agent, and dispersing the mixture evenly at high speed to obtain a PVDF fluorocarbon paint modified by nanoparticles.

[0032] Compared with the prior art, the advantages and beneficial effects of the present invention are:

[0033] 1. The present invention reduces the amount of traditional acrylic emulsion added and adds water-based epoxy resin emulsion at the same time. By compounding water-based PVDF fluorocarbon emulsion, water-based epoxy resin emulsion and acrylic emulsion, the aging resistance of PVDF fluorocarbon paint is significantly improved.

[0034] 2. When using water-based PVDF fluorocarbon emulsion, water-based epoxy resin emulsion and acrylic emulsion with specific parameters, the T-bend performance is improved and the flexibility of the coating is better.

[0035] 3. The present invention improves the moisture and heat resistance of PVDF fluorocarbon paint by modifying the three nanoparticles to obtain modified nanoparticles and adding them into the system.

[0036] 4. The present invention improves the solvent wiping resistance of PVDF fluorocarbon paint by adding a silicon dioxide hyperbranched curing agent, and also improves the impact resistance of PVDF fluorocarbon paint. DETAILED DESCRIPTION

[0037] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] Example 1

[0039] This embodiment provides a PVDF fluorocarbon paint based on nanoparticle modification, comprising the following raw materials in parts by weight: 47 parts of water-based PVDF fluorocarbon emulsion, 25 parts of water-based epoxy resin emulsion, 12 parts of acrylic emulsion, 13 parts of inorganic pigments, 15 parts of modified nanoparticles, 38 parts of film-forming cosolvent, 2 parts of defoamer, 1 part of dispersant, 8 parts of silica hyperbranched curing agent and 33 parts of water;

[0040] The fluorine content of the aqueous PVDF fluorocarbon emulsion is ≥15%, and the solid content is 45±2%. Qingdao Hongfeng Fluorosilicone Technology Co., Ltd., model hfs-f-3301.

[0041] The solid content of the acrylic emulsion is 45±1%, and the glass transition temperature is 20° C. Anhui Zhongen Chemical Co., Ltd., model: PA-511.

[0042] The epoxy equivalent of the waterborne epoxy resin emulsion is 500-600 g / eq, and the viscosity at 25° C. is 1000-6000 mPa·s. Brand: American Hexam Momentive, Model: Epikote6520-WH-53A.

[0043] The film-forming auxiliary solvent is a mixture of propylene glycol methyl ether, ethylene glycol butyl ether and dipropylene glycol methyl ether in a mass ratio of 1:1.4:0.6.

[0044] The inorganic pigment is rutile titanium dioxide.

[0045] The defoamer is BYK-024.

[0046] The dispersant is BYK-190.

[0047] The preparation method of the modified nanoparticles is:

[0048] (1) mixing carbon nanotubes, nano calcium carbonate and DK2 nano montmorillonite in a mass ratio of 1:0.4:1.7 to obtain mixed nanoparticles;

[0049] (2) The ethanol aqueous solution, the mixed nanoparticles and KH-560 in a mass ratio of 9:1:0.2 were stirred evenly, the temperature was raised to 63°C and the reaction was carried out at a constant temperature for 120 minutes, and the filter cake was filtered and dried to obtain the modified nanoparticles.

[0050] The mass concentration of the ethanol aqueous solution is 65%.

[0051] The diameter of carbon nanotubes is 1-2nm, the length is 10-30μm, and the average specific surface area is 1380m 2 / g. Purchased from Xianfeng Nano.

[0052] The particle size of nano calcium carbonate is 0.01-0.1μm and the specific surface area is 20-80m 2 / g.

[0053] DK2 nano-montmorillonite was purchased from Zhejiang Fenghong New Materials Co., Ltd.

[0054] The preparation method of the silicon dioxide hyperbranched curing agent is:

[0055] S1: 1 part by mass of sodium silicate aqueous solution and 4 parts by mass of sulfuric acid solution are added to 12 parts by mass of 53°C water, and the mixture is kept warm for reaction for 8 hours, and then the pH is adjusted to 10 with sodium hydroxide, and 3 parts by mass of calcium chloride are added, and the mixture is heated to 65°C for reaction for 27 hours. After the reaction, the mixture is filtered, washed, dried, and crushed to obtain a calcium ion exchange silica pigment;

[0056] S2: 1 part by mass of calcium ion exchange silica pigment, 0.15 parts by mass of coupling agent KH550 and 7 parts by mass of water were mixed, stirred at 100° C. for 12 h, filtered, washed, dried and crushed to obtain a silica hyperbranched curing agent.

[0057] The mass percentage of sodium silicate in the sodium silicate aqueous solution is 50%.

[0058] H in sulfuric acid solution 2 SO 4 The mass percentage is 55%.

[0059] The preparation method of the above-mentioned nanoparticle-modified PVDF fluorocarbon paint comprises the following steps: adding inorganic pigment, defoamer and dispersant to water in sequence, and dispersing them evenly at high speed; continuing to add water-based PVDF fluorocarbon emulsion, water-based epoxy resin emulsion, acrylic emulsion, inorganic pigment, modified nanoparticles, film-forming cosolvent and silica hyperbranched curing agent, and dispersing them evenly at high speed to obtain nanoparticle-modified PVDF fluorocarbon paint.

[0060] Example 2

[0061] This embodiment provides a PVDF fluorocarbon paint based on nanoparticle modification, comprising the following raw materials in parts by weight: 45 parts of water-based PVDF fluorocarbon emulsion, 27 parts of water-based epoxy resin emulsion, 10 parts of acrylic emulsion, 14 parts of inorganic pigments, 12 parts of modified nanoparticles, 40 parts of film-forming cosolvent, 1 part of defoamer, 3 parts of dispersant, 6 parts of silica hyperbranched curing agent and 35 parts of water;

[0062] The fluorine content of the aqueous PVDF fluorocarbon emulsion is ≥15%, and the solid content is 45±2%. Qingdao Hongfeng Fluorosilicone Technology Co., Ltd., model hfs-f-3301.

[0063] The solid content of the acrylic emulsion is 45±1%, and the glass transition temperature is 20° C. Anhui Zhongen Chemical Co., Ltd., model: PA-511.

[0064] The epoxy equivalent of the waterborne epoxy resin emulsion is 500-600 g / eq, and the viscosity at 25° C. is 1000-6000 mPa·s. Brand: American Hexam Momentive, Model: Epikote6520-WH-53A.

[0065] The film-forming auxiliary solvent is a mixture of propylene glycol methyl ether, ethylene glycol butyl ether and dipropylene glycol methyl ether in a mass ratio of 1:1.3:0.8.

[0066] The inorganic pigment is rutile titanium dioxide.

[0067] The defoamer is BYK-024.

[0068] The dispersant is BYK-190.

[0069] The preparation method of the modified nanoparticles is:

[0070] (1) mixing carbon nanotubes, nano calcium carbonate and DK2 nano montmorillonite in a mass ratio of 1:0.2:1.8 to obtain mixed nanoparticles;

[0071] (2) The ethanol aqueous solution, the mixed nanoparticles and KH-560 in a mass ratio of 10:1:0.2 were stirred evenly, the temperature was raised to 65°C and the reaction was carried out at a constant temperature for 100 minutes, and the filter cake was filtered and dried to obtain the modified nanoparticles.

[0072] The mass concentration of the ethanol aqueous solution is 70%.

[0073] The diameter of carbon nanotubes is 1-2nm, the length is 10-30μm, and the average specific surface area is 1380m 2 / g. Purchased from Xianfeng Nano.

[0074] The particle size of nano calcium carbonate is 0.01-0.1μm and the specific surface area is 20-80m 2 / g.

[0075] DK2 nano-montmorillonite was purchased from Zhejiang Fenghong New Materials Co., Ltd.

[0076] The preparation method of the silicon dioxide hyperbranched curing agent is:

[0077] S1: Add 1 part by mass of sodium silicate aqueous solution and 5 parts by mass of sulfuric acid solution to 15 parts by mass of 50°C water, keep warm for 10 hours, then adjust the pH to 11 with sodium hydroxide, add 2 parts by mass of calcium chloride, heat to 70°C and react for 25 hours, filter, wash, dry and crush after the reaction to obtain calcium ion exchange silica pigment;

[0078] S2: 1 part by mass of calcium ion exchange silica pigment, 0.1 part by mass of coupling agent KH550 and 6 parts by mass of water were mixed, stirred at 100° C. for 10 h, filtered, washed, dried and crushed to obtain a silica hyperbranched curing agent.

[0079] The mass percentage of sodium silicate in the sodium silicate aqueous solution is 55%.

[0080] H in sulfuric acid solution 2 SO 4 The mass percentage is 50%.

[0081] The preparation method of the above-mentioned nanoparticle-modified PVDF fluorocarbon paint comprises the following steps: adding inorganic pigment, defoamer and dispersant to water in sequence, and dispersing them evenly at high speed; continuing to add water-based PVDF fluorocarbon emulsion, water-based epoxy resin emulsion, acrylic emulsion, inorganic pigment, modified nanoparticles, film-forming cosolvent and silica hyperbranched curing agent, and dispersing them evenly at high speed to obtain nanoparticle-modified PVDF fluorocarbon paint.

[0082] Comparative Example 1

[0083] The difference between this comparative example and Example 1 is that the proportions of the water-based PVDF fluorocarbon emulsion, the water-based epoxy resin emulsion and the acrylic emulsion are different.

[0084] A nanoparticle-modified PVDF fluorocarbon paint comprises the following raw materials in parts by weight: 55 parts of water-based PVDF fluorocarbon emulsion, 10 parts of water-based epoxy resin emulsion, 19 parts of acrylic emulsion, 13 parts of inorganic pigments, 15 parts of modified nanoparticles, 38 parts of film-forming cosolvents, 2 parts of defoamers, 1 part of dispersants, 8 parts of silica hyperbranched curing agents and 33 parts of water.

[0085] Comparative Example 2

[0086] The difference between this comparative example and Example 1 is that the mass ratio of carbon nanotubes, nano-calcium carbonate and DK2 nano-montmorillonite is 1:1:1.

[0087] Comparative Example 3

[0088] The difference between this comparative example and Example 1 is that the diameter of the carbon nanotubes is 5-10 nm, the length is 20-40 μm, and the average specific surface area is 670 m 2 / g. Purchased from Xianfeng Nano.

[0089] The particle size of nano calcium carbonate is 0.2-0.5μm and the specific surface area is 5-24m 2 / g.

[0090] DK2 nano-montmorillonite was replaced with DK1 nano-montmorillonite from Zhejiang Fenghong New Materials Co., Ltd.

[0091] Comparative Example 4

[0092] The difference between this comparative example and Example 1 is that the epoxy equivalent of the waterborne epoxy resin emulsion is 195-210, and the viscosity at 25° C. is 15000-25000 mPa·s. Brand: American Hexam Momentive, model: Epikote WD-52A.

[0093] Comparative Example 5

[0094] The difference between this comparative example and Example 1 is:

[0095] The aqueous PVDF fluorocarbon emulsion has a fluorine content of 10±1% and a solid content of 45±1%. Jining Fangyu Chemical Co., Ltd., model: CF-801.

[0096] Comparative Example 6

[0097] The difference between this comparative example and Example 1 is:

[0098] The solid content of the acrylic emulsion is 40-50%, and the glass transition temperature is 6° C. Zhishun ZS-9890H.

[0099] Comparative Example 7

[0100] The difference between this comparative example and Example 1 is that the silica hyperbranched curing agent is replaced with a commercially available waterborne epoxy resin curing agent purchased from Green Union (Jining) Chemical Technology Co., Ltd., model 00178.

[0101] Performance Testing

[0102] The performance tests were performed on the PVDF fluorocarbon paints of Examples 1-2 and Comparative Examples 1-7:

[0103] Refer to HG / T3793-2019 to determine the artificial weathering resistance, impact resistance, solvent wiping resistance, and moisture and heat resistance experiments.

[0104] The water resistance was determined according to GB / T1733-1993.

[0105] Refer to HG / T3830-2022 and conduct T-bend test.

[0106] Table 1 Performance test results

[0107]

[0108]

[0109] From the above performance test results, it can be seen that the nanoparticle-modified PVDF fluorocarbon paints of Examples 1-2 have excellent comprehensive performance, especially Example 1 has the most outstanding comprehensive performance. This is mainly because multiple raw materials synergistically enhance the comprehensive performance of PVDF fluorocarbon paint.

[0110] However, the comparative examples are obviously inferior to the embodiments in the corresponding performance tests because they do not adopt the necessary technical solutions. In comparative example 1, the ratio of the three emulsions is changed, and it can be seen that the anti-aging effect is reduced, proving that the specific ratio compounding scheme of the three emulsions has an important influence on the anti-aging effect. In comparative examples 2-3, the scheme of modified nanoparticles is not used, and it can be seen from the results that the effect of moisture and heat resistance is reduced. Comparative example 7 does not use silica hyperbranched curing agent, and the solvent wiping resistance of PVDF fluorocarbon paint is reduced. The above experimental results further prove the importance of the technical solution defined in the present invention for its technical effect.

[0111] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A PVDF fluorocarbon paint based on nanoparticle modification, characterized in that: The invention comprises the following raw materials in parts by weight: 45-50 parts of water-based PVDF fluorocarbon emulsion, 20-27 parts of water-based epoxy resin emulsion, 10-15 parts of acrylic emulsion, 10-14 parts of inorganic pigment, 12-17 parts of modified nanoparticles, 35-40 parts of film-forming cosolvent, 1-2 parts of defoamer, 1-3 parts of dispersant, 6-10 parts of silica hyperbranched curing agent and 30-35 parts of water; The preparation method of the modified nanoparticles is: (1) mixing carbon nanotubes, nano calcium carbonate and DK2 nano montmorillonite in a mass ratio of 1:0.2-0.5:1.5-1.8 to obtain mixed nanoparticles; (2) Stirring the ethanol aqueous solution, the mixed nanoparticles and KH-560 in a mass ratio of 8-10:1:0.2-0.3 evenly, heating to 60-65°C for constant temperature reaction for 100-150 minutes, filtering, and drying the filter cake to obtain modified nanoparticles; The preparation method of the silicon dioxide hyperbranched curing agent is: S1: Add 1 part by mass of sodium silicate aqueous solution and 3-5 parts by mass of sulfuric acid solution to 10-15 parts by mass of 50-55°C water, keep warm and react for 6-10 hours, then adjust the pH to 10-11 with sodium hydroxide, add 2-4 parts by mass of calcium chloride, heat to 60-70°C and react for 25-30 hours, filter, wash, dry and crush after the reaction to obtain calcium ion exchange silica pigment; S2: Mix 1 part by mass of calcium ion exchange silica pigment, 0.1-0.2 parts by mass of coupling agent KH550 and 6-8 parts by mass of water, stir at 100° C. for 10-15 hours, filter, wash, dry and crush to obtain a silica hyperbranched curing agent; The diameter of carbon nanotubes is 1-2nm, the length is 10-30μm, and the average specific surface area is 1380m 2 / g, purchased from Xianfeng Nano; The particle size of nano calcium carbonate is 0.01-0.1μm and the specific surface area is 20-80m 2 / g; The fluorine content in the water-based PVDF fluorocarbon emulsion is ≥15%, and the solid content is 45±2%; The acrylic emulsion has a solid content of 45±1% and a glass transition temperature of 20°C; The epoxy equivalent of the waterborne epoxy resin emulsion is 500-600 g / eq, and the viscosity at 25° C. is 1000-6000 mPa·s.

2. The nanoparticle-modified PVDF fluorocarbon paint according to claim 1, characterized in that: The mass percentage of sodium silicate in the sodium silicate aqueous solution is 40-55%.

3. The nanoparticle-modified PVDF fluorocarbon paint according to claim 1, characterized in that: The mass percentage of H2SO4 in sulfuric acid solution is 50-60%.

4. The nanoparticle-modified PVDF fluorocarbon paint according to claim 1, characterized in that: The mass concentration of the ethanol aqueous solution is 60-70%.

5. The nanoparticle-modified PVDF fluorocarbon paint according to claim 1, characterized in that: The film-forming auxiliary solvent is a mixture of propylene glycol methyl ether, ethylene glycol butyl ether and dipropylene glycol methyl ether in a mass ratio of 1:1.3-1.6:0.5-0.

8.

6. A method for preparing a nanoparticle-modified PVDF fluorocarbon paint according to any one of claims 1 to 5, characterized in that: The preparation method comprises the following steps: adding inorganic pigment, defoamer and dispersant into water in sequence, and dispersing evenly at high speed; and continuously adding water-based PVDF fluorocarbon emulsion, water-based epoxy resin emulsion, acrylic emulsion, inorganic pigment, modified nanoparticles, film-forming cosolvent and silica hyperbranched curing agent, and dispersing evenly at high speed to obtain PVDF fluorocarbon paint based on nanoparticle modification.

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