Modified composite powder, preparation method and electrophoretic paint containing the modified composite powder

Abstract

The application discloses a modified composite powder, a preparation method of the modified composite powder and electrophoretic paint containing the modified composite powder. The modified composite powder is composed of the following components in mass fraction: 10-15 parts of deionized water, 0.05-0.15 parts of a surfactant FS-3100, 4.5-6.2 parts of silica sol, 0.9-1.1 parts of ammonia water, 2.5-3 parts of round flake diatomite, 0.2 parts of graphene oxide, 0.1-0.2 parts of nano zinc particles, 0.5-0.9 parts of Al(OH)3, 0.5-0.9 parts of perfluorodecyl triethoxysilane and 0.5-0.9 parts of a silane coupling agent. The diatomite particles are inhomogeneously modified by using hydrophobic silane molecules and hydrophilic silane coupling agent molecules, the hydrophobic groups and the hydrophilic groups are simultaneously introduced on the surface of the diatomite particles, the high compatibility between the powder filler and the resin matrix is realized while the superhydrophobicity of the powder filler is ensured, and the water resistance, the corrosion resistance and the moisture and heat resistance of the coating are effectively improved.

Description

TECHNICAL FIELD

[0001] The present application relates to a modified composite powder, and also relates to a preparation method of the modified composite powder and an electrophoretic paint containing the modified composite powder. BACKGROUND

[0002] In the electrophoretic paint industry, powder fillers as an important paint raw material can provide some properties required by the coating, such as corrosion resistance, wear resistance and mechanical strength. However, due to the strong water absorption of traditional powder fillers, the compatibility with the resin matrix is insufficient, which affects the water resistance, corrosion resistance and moisture resistance of the coating. Many researchers propose to modify the powder fillers to be super-hydrophobic, for example, in the patent CN116814110A, the particles are modified to be super-hydrophobic / super-oleophobic, thereby improving the wear resistance and anti-fouling performance of the coating. However, due to the large interfacial tension difference between the hydrophobic modified powder particles and the dispersed resin, the particles tend to aggregate rather than disperse in the resin, thereby causing the electrophoretic paint to be prone to aggregation. Therefore, how to realize the good dispersion of the powder filler in the electrophoretic paint has become a key technical problem to be solved. SUMMARY

[0003] The purpose of the present application is to provide a modified composite powder, which is modified by using hydrophobic silane molecules and hydrophilic silane coupling agent molecules to modify diatomite particles heterogeneously, so that the surface of the diatomite particles presents a heterogeneous modification of hydrophilic molecules and hydrophobic molecules, which can effectively reduce the water absorption of the modified composite powder and strengthen its mechanical properties. The heterogeneously modified composite powder has good dispersibility in the electrophoretic paint and good compatibility with the resin, thereby improving the stability of the electrophoretic paint and the density and mechanical strength of the electrophoretic coating. Another purpose of the present application is to provide a preparation method of the modified composite powder and an electrophoretic paint containing the modified composite powder.

[0004] Technical scheme: The modified composite powder according to the present application is composed of the following components in mass fraction: 10-15 parts of deionized water, 0.05-0.15 parts of surfactant FS-3100, 4.5-6.2 parts of silica sol, 0.9-1.1 parts of ammonia water, 2.5-3 parts of round flaky diatomite, 0.2 parts of graphene oxide, 0.1-0.2 parts of nano zinc particles, 0.5-0.9 parts of Al(OH)3, 0.5-0.9 parts of perfluorodecyltriethoxysilane and 0.5-0.9 parts of silane coupling agent.

[0005] The particle size of the silica sol is 5-20 nm; the solid content is 10wt.%-35wt.%; the mass fraction of the ammonia water is 25%-28%; the particle size of the round flaky diatomite particles is 7-13μm; and the diatomite selected in the present application is purchased from NanYu Mining and then sieved.

[0006] The structure of the modified composite powder is a porous disc; and the particle size of the modified composite powder is 10-13 microns.

[0007] The surface of the silica tetrahedron of diatomite contains a large number of hydroxyl groups (-OH), which can interact with silane coupling agents through hydrogen bonds, and realize the heterogeneous modification of hydrophilic molecules and hydrophobic molecules through covalent bonding reaction; at the same time, the introduction of Al(OH)3 modifies and chemically reacts with the hydroxyl groups on the surface of diatomite, thereby improving the reactivity and hydroxyl content; and the physical adsorption of zinc powder and graphene on the surface of diatomite forms a carbon-based layer and zinc hydroxide under certain conditions, thereby further enhancing the corrosion resistance and stability of the modified composite powder.

[0008] The preparation method of the modified composite powder is as follows: deionized water, FS-3100, ammonia water and perfluorodecyl triethoxysilane are sequentially added to a reaction container in a formula amount, stirring is started and the temperature is raised to 50-60 DEG C, and then the silica sol, diatomite and Al(OH)3 are added in a formula amount under heat preservation and stirring is uniform; then the graphene oxide and nano zinc particles are added in a formula amount, and the stirring is continued; finally, the silane coupling agent is added, and the stirring is continued for 12-36 hours, so that the diatomite particles are simultaneously modified by the hydrophobic silane molecules and the hydrophilic silane coupling agent molecules (KH550), and after the reaction, the diatomite particles are dried and ground to 1000 mesh to obtain the heterogeneous modified composite powder.

[0009] The electrophoretic paint containing the modified composite powder is prepared by the following method: 4.5-10 parts by mass of the modified composite powder, 35-49 parts by mass of the dispersing resin, 1.8-3.0 parts by mass of carbon black, 10-20 parts by mass of kaolin and 1-1.5 parts by mass of the wet dispersing agent (Digo 750w) are mixed, and then sufficient deionized water is added, and the mixture is ground to a particle size of less than 17.5 microns, and finally deionized water is added to dilute the mixture to a solid content of 45-50%, thereby obtaining a black color paste; 30-80 parts by mass of the color paste, 300 parts by mass of the HLS-1701BLB emulsion (HLS product) and 400-650 parts by mass of deionized water are mixed to obtain the electrophoretic paint.

[0010] The black color paste prepared by the method is a yogurt-like liquid, and the inside is charged particles with a particle size of about 10 microns, which will not settle.

[0011] The dispersing resin is a quaternary ammonium salt type grinding resin, which is prepared by the method reported in Chinese patent 202011179699.4.

[0012] The solid content of the electrophoretic paint is 8-15%.

[0013] In the electrophoretic paint, the positively charged quaternary ammonium salt grinding resin is combined with the negatively charged modified composite powder, and the combination is due to the mutual attraction between the positive and negative charges and the bridging effect of the hydrophilic molecules of the surface grafted silane coupling agent, thereby significantly enhancing the compactness and mechanical strength of the coating.

[0014] The method for forming an electrophoretic coating based on the above electrophoretic paint is as follows: the prepared electrophoretic paint is placed in an electrophoresis tank for electrophoretic deposition, with a stainless steel plate as the anode and the workpiece as the cathode, an electrophoretic voltage of 100-220 V, an electrophoretic temperature of 28-32 DEG C, and an electrophoretic time of 30-180 s, to obtain a corrosion-resistant electrophoretic coating on the workpiece.

[0015] The diatomite particles are modified by using hydrophobic silane molecules and hydrophilic silane coupling agent molecules, so that hydrophobic groups and hydrophilic groups are introduced on the surfaces of the diatomite particles, the compatibility of the modified composite powder with the resin matrix is improved, and the water resistance, corrosion resistance and moisture resistance of the coating are effectively improved.

[0016] Compared with the prior art, the present application has the following advantages: (1) the diatomite is modified by using hydrophobic silane molecules and hydrophilic silane coupling agent molecules, so that the diatomite microshell surface has active groups and low surface energy groups, the diatomite surface contains both hydrophilic and hydrophobic molecules, the interface bonding force is improved by dehydration condensation between the diatomite and the resin to form new covalent bonds, and the durability and environmental stability of the coating are improved; (2) the compatibility of the modified composite powder with the resin matrix is further improved by introducing aluminum hydroxide, zinc powder and graphene, and the water resistance, corrosion resistance and moisture resistance of the coating are effectively improved; (3) the one-step electrophoretic method has the advantages of high efficiency and low cost, and is not limited by the shape of the workpiece; the surface of the prepared super-hydrophobic electrophoretic coating is covered with low surface energy and low chemical activity groups, the inside is crosslinked by high-energy covalent bonds, a continuous and dense structure of the coating is achieved, and good mechanical strength and corrosion resistance are ensured; (4) the diatomite is modified by using hydrophilic and hydrophobic molecules, and can be uniformly dispersed in the resin matrix, the stability of the coating is improved (no sedimentation after 7 days of hot storage at 50 DEG C), the neutral salt spray performance of the coating is improved by 108.33%, the water resistance can reach 80 DEG C for 168 h, the adhesion is 0 grade, and the moisture resistance can last for 7 days according to the GB / T 1740-2007 standard without any change. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 (a) is a surface scanning diagram of the electrophoretic coating of Example 3; (b) is a surface scanning diagram of the electrophoretic coating of Comparative Example 6;

[0018] Figure 2 Appearance pictures of the phosphating plates of the paint films prepared in Examples 1-3 and the phosphating plates of the paint films of Comparative Examples 4-6 after immersion in a 5wt% NaCl environment at 80℃ for 7 days;

[0019] Figure 3 Appearance pictures of the phosphating plates of the paint films prepared in Examples 1-3 and the phosphating plates of the paint films of Comparative Examples 4-6 after neutral salt spray test according to GB / T10125-2021 standard. DETAILED DESCRIPTION

[0020] Example 1

[0021] The modified composite powder of the application is composed of the following components in mass fraction: 15 parts of deionized water, 0.15 parts of FS-3100, 6.2 parts of silica sol, 1.0 parts of ammonia water, 3 parts of round flaky diatomite, 0.2 parts of graphene oxide, 0.2 parts of nano zinc particles, 0.9 parts of Al(OH)3, 0.9 parts of perfluorodecyl triethoxysilane, and 0.9 parts of silane coupling agent.

[0022] The particle size of the silica sol is 7-15 nm; the solid content is 15wt.%; the mass fraction of the ammonia water is 25%-28%; and the particle size of the round flaky diatomite is 7-13 μm.

[0023] The preparation method of the modified composite powder is as follows: the formula amount of deionized water, FS-3100, ammonia water, and perfluorodecyl triethoxysilane are sequentially added to a reaction container, stirring is started and the temperature is raised to 50℃; then the formula amount of silica sol, diatomite, and Al(OH)3 is added, and stirring is uniform; then the formula amount of graphene oxide and nano zinc particles is added, and stirring is continued for 30 min; finally, the formula amount of silane coupling agent is added, and stirring is continued for 36 h; finally, drying and grinding to 1000 mesh are performed to obtain the heterogeneous modified composite powder.

[0024] The electrophoretic paint containing the modified composite powder is prepared by the following method: 10 parts by mass of the modified composite powder, 49 parts by mass of a quaternary ammonium salt type grinding resin, 3.0 parts by mass of carbon black, 10 parts by mass of kaolin, and 1.5 parts by mass of a wet dispersant (Digo 750w) are mixed, and a sufficient amount of deionized water is added, and grinding is performed to a particle fineness of <17.5 μm, and finally deionized water is added to dilute to a solid content of 45%, to obtain a black color paste; 30 parts by mass of the color paste, 300 parts by mass of HLS-1701BLB emulsion (HLS product), and 550 parts by mass of deionized water are mixed to obtain an electrophoretic paint; the solid content of the electrophoretic paint is 13%.

[0025] The method for forming an electrophoretic coating based on the electrophoretic paint is as follows: the prepared electrophoretic paint is placed in an electrophoretic tank for electrophoretic deposition, a stainless steel plate is used as an anode, an electrophoretic workpiece is used as a cathode, an electrophoretic voltage is 220 V, an electrophoretic temperature is 32 DEG C, and an electrophoretic time is 90 s, so that a corrosion-resistant electrophoretic coating is obtained on the workpiece. The workpiece needs to be degreased before electrophoresis, and no other pretreatment process is needed.

[0026] The water contact angle of the heterogeneous modified composite powder prepared in Example 1 is 160 DEG C, the modified composite powder particles aggregate in the resin system, the prepared color paste is deposited after being stored for 2 days at room temperature, and the coating surface has a particle feeling.

[0027] Example 2

[0028] The modified composite powder comprises the following components in mass fractions: 10 parts of deionized water, 0.05 parts of FS-3100, 6.2 parts of silica sol, 1.1 parts of ammonia water, 2.5 parts of round flaky diatomite, 0.2 parts of graphene oxide, 0.1 parts of nano zinc particles, 0.5 parts of Al(OH)3, 0.5 parts of perfluorodecyl triethoxysilane, and 0.5 parts of silane coupling agent.

[0029] The particle size of the silica sol is 7-15 nm, the solid content is 15 wt.%, the mass fraction of the ammonia water is 25%-28%, and the particle size of the round flaky diatomite is 7-13 mu m.

[0030] The preparation method of the modified composite powder is as follows: the formula amount of deionized water, FS-3100, ammonia water and perfluorodecyl triethoxysilane are sequentially added to a reaction container, stirring is started and the temperature is raised to 50 DEG C; then the formula amount of silica sol, diatomite and Al(OH)3 is added under insulation, and stirring is uniformly performed; then the formula amount of graphene oxide and nano zinc particles is added, and stirring is continuously performed for 30 min; finally, the formula amount of silane coupling agent is added, and stirring is continuously performed for 12 h, and finally, drying and grinding to 1000 mesh are performed to obtain the heterogeneous modified composite powder.

[0031] The electrophoretic paint containing the modified composite powder is prepared by the following method: 10 parts of modified composite powder, 49 parts of quaternary ammonium salt type grinding resin, 3.0 parts of carbon black, 10 parts of kaolin and 1.5 parts of wet dispersant (Digo 750w) are mixed, and sufficient deionized water is added thereto, and grinding is performed to a particle fineness of <17.5 mu m, and finally, deionized water is added to dilute to a solid content of 45%, so that a black color paste is obtained; 30 parts of the color paste, 300 parts of HLS-1701BLB emulsion (HLS product) and 500 parts of deionized water are mixed to obtain an electrophoretic paint; and the solid content of the electrophoretic paint is 13%.

[0032] The method for forming the electrophoretic coating based on the electrophoretic paint is specifically as follows: the prepared electrophoretic paint is placed in an electrophoretic tank for electrophoretic deposition, a stainless steel plate is used as an anode, an electrophoretic workpiece is used as a cathode, an electrophoretic voltage is 220 V, an electrophoretic temperature is 32 DEG C, and an electrophoretic time is 60 s, so that a corrosion-resistant electrophoretic coating is obtained on the workpiece. The workpiece needs to be degreased before electrophoresis, and no other pretreatment process is needed.

[0033] The water contact angle of the heterogeneous modified composite powder prepared in the embodiment 2 is 130 DEG C. The surface of the modified composite powder is regulated by hydrophobic / hydrophilic groups, and the compatibility with the resin is improved compared with that in the embodiment 1. The prepared colorant is stored for 4 days at room temperature and then is settled, but the coating surface still has a granular feeling.

[0034] Embodiment 3

[0035] The modified composite powder comprises the following components in mass fractions: 15 parts of deionized water, 0.1 part of FS-3100, 4.5 parts of silica sol, 0.9 parts of ammonia water, 3 parts of round flaky diatomite, 0.2 part of graphene oxide, 0.2 part of nano zinc particles, 0.7 part of Al(OH)3, 0.9 part of perfluorodecyl triethoxysilane and 0.9 part of silane coupling agent.

[0036] The particle size of the silica sol is 7-15 nm, the solid content is 15 wt.%, the mass fraction of the ammonia water is 25%-28%, and the particle size of the round flaky diatomite is 7-13 mu m.

[0037] The preparation method of the modified composite powder is specifically as follows: the formula amount of deionized water, FS-3100, ammonia water and perfluorodecyl triethoxysilane are sequentially added to a reaction container, stirring is started and the temperature is raised to 50 DEG C; then the formula amount of silica sol, diatomite and Al(OH)3 is added under insulation, and stirring is uniformly performed; then the formula amount of graphene oxide and nano zinc particles is added, and stirring is continuously performed for 30 min; finally, the formula amount of silane coupling agent is added, and stirring is continuously performed for 24 h, and finally, drying and grinding to 1000 mesh are performed to obtain the heterogeneous modified composite powder.

[0038] The electrophoretic paint containing the modified composite powder is prepared by the following method: 4.5 parts by mass of the modified composite powder, 49 parts by mass of a quaternary ammonium salt type grinding resin, 3.0 parts by mass of carbon black, 15.5 parts by mass of kaolin and 1.5 parts by mass of a wet dispersant (Digo 750w) are mixed, and sufficient deionized water is added thereto, and grinding is performed to a particle fineness of <17.5 mu m, and finally, deionized water is added to dilute to a solid content of 45%, so that a black colorant is obtained; 30 parts by mass of the colorant, 300 parts by mass of HLS-1701BLB emulsion (HLS product) and 500 parts by mass of deionized water are mixed, so that an electrophoretic paint is obtained; and the solid content of the electrophoretic paint is 13%.

[0039] The method for forming the electrophoretic coating based on the electrophoretic paint is specifically as follows: the prepared electrophoretic paint is placed in an electrophoretic tank for electrophoretic deposition, a stainless steel plate is used as an anode, an electrophoretic workpiece is used as a cathode, an electrophoretic voltage is 220 V, an electrophoretic temperature is 32 DEG C, and an electrophoretic time is 60 s, so that a corrosion-resistant electrophoretic coating is obtained on the workpiece. The workpiece needs to be degreased before electrophoresis, and no other pretreatment process is needed.

[0040] The water contact angle of the heterogeneous modified composite powder prepared in Example 3 is 150 DEG C, the prepared color paste does not settle after being stored at room temperature and hot storage (50 DEG C) for 7 days, and the coating surface is smooth. Therefore, by changing the ratio of the hydrophobic group and the hydrophilic group on the surface of the modified particles, the difference in interfacial tension between the modified particles and the dispersed resin can be reduced, and the performance and coating effect of the electrophoretic paint can be improved.

[0041] Comparative Example 4

[0042] The modified composite powder of the application is composed of the following components in mass fraction: 15 parts of deionized water, 0.1 parts of FS-3100, 4.5 parts of silica sol, 0.9 parts of ammonia water, 3 parts of round flaky diatomite, 0.2 parts of graphene oxide, 0.2 parts of nano zinc particles, 0.9 parts of perfluorodecyl triethoxysilane and 0.9 parts of silane coupling agent.

[0043] The particle size of the silica sol is 7-15 nm, the solid content is 15 wt.%, the mass fraction of the ammonia water is 25%-28%, and the particle size of the round flaky diatomite is 7-13 μm.

[0044] The preparation method of the modified composite powder is specifically as follows: the formula amount of deionized water, FS-3100, ammonia water and perfluorodecyl triethoxysilane are sequentially added to a reaction container, stirring is started and the temperature is raised to 50 DEG C; then the formula amount of silica sol and diatomite is added under insulation, and stirring is uniform; then the formula amount of graphene oxide and nano zinc particles is added, and stirring is continued for 30 min; finally, the formula amount of silane coupling agent is added, and stirring is continued to react for 24 h; finally, drying and grinding to 1000 mesh are performed to obtain the heterogeneous modified composite powder.

[0045] The electrophoretic paint containing the modified composite powder is prepared by the following method: 4.5 parts by mass of the modified composite powder, 49 parts by mass of a quaternary ammonium salt type grinding resin, 3.0 parts by mass of carbon black, 15.5 parts by mass of kaolin and 1.5 parts by mass of a wet dispersant (Digo 750w) are mixed, a sufficient amount of deionized water is added thereto, grinding is performed to a particle fineness of <17.5 μm, finally deionized water is added to dilute to a solid content of 45%, and a black color paste is obtained; 30 parts by mass of the color paste, 300 parts by mass of HLS-1701BLB emulsion (HLS product) and 500 parts by mass of deionized water are mixed to obtain an electrophoretic paint; and the solid content of the electrophoretic paint is 13%.

[0046] The method for forming an electrophoretic coating based on the above electrophoretic paint is as follows: the prepared electrophoretic paint is put into an electrophoresis tank for electrophoretic deposition, with a stainless steel plate as an anode and a workpiece as a cathode, an electrophoretic voltage of 220 V, an electrophoretic temperature of 32°C, and an electrophoretic time of 60 s, so as to obtain a corrosion-resistant electrophoretic coating on the workpiece. The workpiece needs to be degreased before electrophoresis, and no other pretreatment process is required.

[0047] The water contact angle of the heterogeneous modified composite powder prepared in Comparative Example 4 is 160°C, the modified composite powder particles are uniformly mixed with the resin, the prepared color paste does not settle at room temperature and hot storage (50°C) for 7 days, and the coating surface is smooth.

[0048] Comparative Example 5

[0049] A preparation method of an electrophoretic paint is as follows: 49 parts by mass of a quaternary ammonium salt type grinding resin, 3.0 parts by mass of carbon black, 20 parts by mass of kaolin, and 1.5 parts by mass of a wet dispersant (Digo 750w) are mixed, and a sufficient amount of deionized water is added and ground to a particle fineness of <17.5 μm, and finally deionized water is added to dilute to a solid content of 45%, to obtain a black color paste; 30 parts by mass of the color paste, 300 parts by mass of HLS-1701BLB emulsion (HLS product), and 500 parts by mass of deionized water are mixed, to obtain an electrophoretic paint; and the solid content of the electrophoretic paint is 13%.

[0050] The method for forming an electrophoretic coating based on the above electrophoretic paint is as follows: the prepared electrophoretic paint is put into an electrophoresis tank for electrophoretic deposition, with a stainless steel plate as an anode and a workpiece as a cathode, an electrophoretic voltage of 220 V, an electrophoretic temperature of 32°C, and an electrophoretic time of 60 s, so as to obtain a corrosion-resistant electrophoretic coating on the workpiece.

[0051] The color paste prepared in Comparative Example 5 does not settle at room temperature and hot storage (50°C) for 7 days, and the coating surface is smooth.

[0052] Comparative Example 6

[0053] The super-amphiphobic porous powder of Example 3 of Chinese patent CN116814110A is selected: 5 parts of silica sol, 4 parts of ammonia water, 0.4 parts of perfluorodecyl triethoxysilane and 0.3 parts of surfactant are sequentially added into 80 parts of deionized water under a constant temperature water bath of 50℃, and magnetic stirring is performed for 10h to obtain a modified nanoparticle suspension; the nanoparticle is a silica nanoparticle; the surfactant is fluorocarbon surfactant FS-30; 0.6 parts of perfluorodecyl triethoxysilane, 0.7 parts of aluminum hydroxide and 3 parts of microporous particles are sequentially added into the modified nanoparticle suspension, and magnetic stirring is performed for 10h to obtain a nanoparticle-loaded porous particle suspension; the microporous particle is diatomite; the nanoparticle-loaded microporous powder is obtained by drying the nanoparticle-loaded porous particle suspension at 180℃ for 4h; and the particle size of the nanoparticle-loaded microporous powder is 20-30μm.

[0054] The electrophoretic paint containing the super-amphiphobic porous powder is prepared by the following method: 4.5 parts by mass of microporous diatomite powder, 49 parts by mass of quaternary ammonium salt type grinding resin, 3.0 parts by mass of carbon black, 15.5 parts by mass of kaolin and 1.5 parts by mass of wet dispersant (Digo 750w) are mixed, and a sufficient amount of deionized water is added thereto, and grinding is performed until the particle fineness is <17.5μm, and finally deionized water is added for dilution until the solid content is 45%, to obtain a black color paste; 30 parts by mass of the color paste, 300 parts by mass of HLS-1701BLB emulsion (HLS product) and 550 parts by mass of deionized water are mixed to obtain an electrophoretic paint; and the solid content of the electrophoretic paint is 15%.

[0055] The method for forming an electrophoretic coating layer based on the above electrophoretic paint is as follows: the prepared electrophoretic paint is placed in an electrophoresis tank for electrophoretic deposition, a stainless steel plate is used as the anode, and the workpiece is used as the cathode, the electrophoretic voltage is 220V, the electrophoretic temperature is 32℃, and the electrophoretic time is 60s, to obtain a corrosion-resistant electrophoretic coating layer on the workpiece.

[0056] The microporous diatomite powder obtained in Comparative Example 6 has a water contact angle of 157℃, the modified diatomite particles are not uniformly mixed with the resin, the prepared color paste is deposited after being stored at room temperature for 2 days, and the coating layer surface is rough.

[0057] The paint film phosphatized plates prepared in Examples 1-3 and the paint film phosphatized plates prepared in Comparative Examples 4-6 are compared in terms of appearance performance and mechanical properties, wherein the adhesion test is tested according to the GB / T 9286-1998 standard, the salt water resistance test is immersed in an environment of 80℃ and 5wt% NaCl for 7 days, the neutral salt spray is tested strictly according to the GB / T 10125-2021 standard, the wet heat resistance is tested strictly according to the GB / T 1740-2007 standard, and the related parameters of the coating layer are shown in Table 1.

[0058] Table 1

[0059]

[0060]

[0061] The present invention utilizes hydrophobic silane molecules and hydrophilic silane coupling agent molecules to simultaneously modify diatomaceous earth particles, resulting in both hydrophobic and hydrophilic groups on the diatomaceous earth particle surface. This allows for improved compatibility and adhesion with resin molecules through covalent bonds and the attractive forces of positive and negative charges, significantly enhancing the adhesion, corrosion resistance, and moisture and heat resistance of the electrophoretic coating. Compared to Comparative Example 5 (without modified particles), the neutral salt spray performance of the coating in Example 3 improved by 108.33%. Furthermore, the coating achieved water resistance of 80°C for 168 hours, with adhesion level 0, and maintained its moisture and heat resistance for up to 7 days according to the GB / T 1740-2007 standard. By comparing Examples 1-3, it was found that the reasonable regulation of the ratio of hydrophobic groups and hydrophilic groups on the surface of the modified particles can improve the dispersion performance of the super-hydrophobic powder filler in the resin, thereby improving the performance and coating effect of the electrophoretic coating; by comparing Example 3 and Comparative Example 4, it was found that the addition of aluminum hydroxide can improve the reaction activity and hydroxyl content, which helps to improve the compatibility of the modified particles with the resin; by comparing Example 3 and Comparative Example 6, it was found that the modified particles of the present invention have better dispersibility in the resin system than the super-hydrophobic particles in the CN116814110A patent.

[0062] Depend on Figure 1 It can be seen that the modified composite powder of Example 3 can be well dispersed in the electrophoretic coating, and the prepared coating is flat and smooth. Figure 2 It can be seen that the coating of Example 3 has excellent water resistance. Figure 3 It can be seen that the coating of Example 3 has excellent neutral salt spray performance.

Claims

1. A modified composite powder, characterized in that: The invention is composed of the following components in parts by mass: 10-15 parts of deionized water, 0.05-0.15 parts of surfactant FS-3100, 4.5-6.2 parts of silica sol, 0.9-1.1 parts of ammonia water, 2.5-3 parts of flaky diatomaceous earth, 0.2 parts of graphene oxide, 0.1-0.2 parts of nano zinc particles, 0.5-0.9 parts of Al(OH)3, 0.5-0.9 parts of perfluorodecyltriethoxysilane and 0.5-0.9 parts of silane coupling agent.

2. The modified composite powder according to claim 1, characterized in that: The particle size of the silica sol is 5~20nm; the solid content is 10wt.%~35wt.%.

3. The modified composite powder according to claim 1, characterized in that: The particle size of the disc-shaped diatomaceous earth particles is 7~13μm.

4. The method for preparing the modified composite powder according to claim 1, characterized in that: Specifically, the following steps are taken: add the formulated amounts of deionized water, FS-3100, ammonia water and perfluorodecyltriethoxysilane to the reaction container in sequence, start stirring and heat to 50-60°C, add the formulated amounts of silica sol, diatomaceous earth and Al(OH)3 while keeping the temperature constant, and stir evenly; then add the formulated amounts of graphene oxide and nano-zinc particles and continue stirring; finally, add the silane coupling agent, continue stirring and reacting for 12-36 hours, dry and grind after the reaction to obtain a heterogeneous modified composite powder.

5. The method for preparing the modified composite powder according to claim 4, wherein: The modified composite powder has a porous disc-shaped structure and a particle size of 10-13 μm.

6. An electrophoretic coating containing the modified composite powder according to claim 1, characterized in that: The electrophoretic coating is prepared by the following method: 4.5-10 parts by mass of modified composite powder, 35-49 parts by mass of dispersion resin, 1.8-3.0 parts by mass of carbon black, 10-20 parts by mass of kaolin and 1-1.5 parts by mass of wetting dispersant are mixed, sufficient amount of deionized water is added, and the mixture is ground to a particle fineness of less than 17.5 μm, and finally deionized water is added to dilute the mixture to a solid content of 45-50% to obtain a black color paste; and 30-80 parts by mass of the black color paste, 300 parts by mass of HLS-1701BLB emulsion and 400-650 parts by mass of deionized water are mixed to obtain an electrophoretic coating.

7. The electrophoretic coating according to claim 6, characterized in that: The solid content of electrophoretic coating is 8~15%.

8. The electrophoretic coating according to claim 6, characterized in that: The dispersing resin is a quaternary ammonium salt grinding resin.

9. The method for forming an electrophoretic coating based on the electrophoretic paint according to claim 6, characterized in that: Specifically, the prepared electrophoretic coating is placed in an electrophoretic tank for electrophoretic deposition, with the stainless steel plate as the anode and the workpiece to be electrophoretically deposited as the cathode. The electrophoretic voltage is 100-220 V, the electrophoretic temperature is 28-32 ° C, and the electrophoretic time is 30-180 s to obtain an electrophoretic coating on the workpiece.

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