A superhydrophobic coating combining a solvent-free anti-corrosion primer and its preparation method

Abstract

This invention discloses a superhydrophobic and oleophobic coating combined with a solvent-free anti-corrosion primer and its preparation method. The superhydrophobic and oleophobic coating includes a solvent-free anti-corrosion primer layer, an intermediate paint layer, and a topcoat layer. The solvent-free anti-corrosion primer layer includes epoxy resin, butyl glycidyl ether, pigments, fillers, and additives. The intermediate paint layer includes fluorocarbon resin, diluent, pigments, fillers, and additives. The topcoat layer includes fumed silica and ethanol. This invention, through the mutual compatibility and synergistic effect of the primer layer, intermediate paint layer, and superhydrophobic topcoat layer, enables the overall coating to not only exhibit excellent hydrophobic and oleophobic properties but also possess long-lasting anti-corrosion performance, extending the service life of the metal substrate. It also improves the hydrophobic and oleophobic stability of the superhydrophobic and oleophobic coating, showing promising application prospects.

Description

Technical Field

[0001] This invention belongs to the field of anti-corrosion coating technology, specifically relating to a superhydrophobic coating combined with a solvent-free anti-corrosion primer and its preparation method. Background Technology

[0002] Superhydrophobic coatings refer to coatings with a static contact angle greater than 150 degrees and a roll-off angle less than 10 degrees with water and oil droplets. They possess waterproof, oil-proof, self-cleaning, and anti-fouling functions, thus having broad application prospects in daily life and industrial fields. Due to their superhydrophobic properties, water droplets carry away dust particles and dirt adhering to the substrate surface as they slide off, thereby achieving a self-cleaning function.

[0003] Currently, commonly available superhydrophobic and oleophobic functional materials are mainly coated on substrates such as metals, glass, and plastics, providing excellent hydrophobic and oleophobic effects. However, due to the low solids content and thin coating, their resistance to water penetration and salt spray is poor, failing to achieve long-term corrosion protection and severely impacting the stability and durability of the superhydrophobic and oleophobic coatings. Particularly on some metal substrates, long-term wetting and penetration by salt spray and water molecules in the air leads to severe chemical and electrochemical corrosion. The spread of corrosion reduces the adhesion between the superhydrophobic and oleophobic material and the metal substrate, eventually causing the coating to crack and peel off, losing its hydrophobic and oleophobic functionality. For example, in the coastal rail transit industry, superhydrophobic and oleophobic coatings are applied to guide rails to prevent dust and water accumulation and to block stray currents. While this provides some hydrophobic and oleophobic effect, it cannot achieve long-term corrosion protection for the guide rails. The super hydrophobic and oleophobic coatings used in electrical boxes and cabinets in the power industry have certain hydrophobic, oleophobic, and anti-condensation capabilities. However, in high-humidity environments, moisture can still penetrate the substrate through the super hydrophobic and oleophobic coating, causing severe corrosion and leading to the peeling off of the super hydrophobic and oleophobic coating, thereby reducing the hydrophobic and oleophobic durability of the super hydrophobic and oleophobic coating.

[0004] Therefore, improving the durability of superhydrophobic materials on metal substrates is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the present invention provides a superhydrophobic coating that combines a solvent-free anti-corrosion primer. When applied to a metal substrate, the coating can adapt well to harsh corrosive environments and meet the requirements for long-term durability.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] A super-hydrophobic coating combining a solvent-free anti-corrosion primer is composed of a solvent-free anti-corrosion primer layer, an intermediate paint layer and a topcoat layer in sequence. The primer layer is composed of a primer base agent and a primer curing agent, the intermediate paint layer is composed of an intermediate paint base agent and an intermediate paint curing agent, and the topcoat layer includes fumed silica and ethanol.

[0008] Specifically, the primer base consists of 30-60% epoxy resin, 5-12% butyl glycidyl ether, 10-40% primer pigment, 10-40% primer filler, and 1.5-6% primer additives, by mass percentage;

[0009] The intermediate paint main agent is composed of 30-50% fluorocarbon resin, 10-20% diluent, 5-25% intermediate paint pigment, 5-25% intermediate paint filler, and 1.5-5% intermediate paint additives, by mass percentage, and the diluent is composed of n-butanol and ethyl acetate.

[0010] Preferably, in the above-mentioned superhydrophobic coating, the topcoat layer is composed of 3-15% fumed silica, 1-2% silane coupling agent, and 83-96% ethanol, by mass percentage.

[0011] Preferably, in the above-mentioned superhydrophobic coating, the primer main agent is bisphenol A resin E51, and the primer curing agent is cashew oil modified phenolic amine curing agent. In this preferred embodiment, because the bisphenol A epoxy resin E51 contains a large number of polar groups such as hydroxyl and ether groups in its molecular structure, during the cross-linking and curing process with the cashew oil-modified phenolic amine curing agent, the active hydroxyl groups in the molecule react with the atoms of the interfacial metal substrate to form very stable chemical bonds. This ensures that the cured coating has extremely strong adhesion to the metal substrate. In addition, the high cross-linking density and the rigid benzene ring structure in the molecular chain give the coating excellent physical and mechanical properties such as wear resistance, impact resistance, collision resistance, and scratch resistance. The cashew oil-modified phenolic amine curing agent contains a long carbon-15 chain with unsaturated double bonds. After the cross-linking and curing reaction with the bisphenol A epoxy resin E51, the curing shrinkage rate is small, and the coating structure is extremely dense. This gives the coating excellent corrosion resistance properties such as acid resistance, alkali resistance, fresh water immersion resistance, seawater immersion resistance, salt spray resistance, and cathodic disbondment resistance. Even in harsh corrosive environments, the metal substrate still has extremely long-term corrosion resistance.

[0012] Preferably, in the above-mentioned superhydrophobic coating, the primer pigment is rutile titanium dioxide and / or iron oxide black, and the primer filler is one or more of kaolin, talc, mica, barium sulfate, and feldspar.

[0013] Preferably, in the above-mentioned superhydrophobic coating, the primer additive is one or more of the following: rheology modifier, dispersant, leveling agent, defoamer, and silane coupling agent.

[0014] More preferably, the primer additives consist of a rheology modifier, a dispersant, a leveling agent, a defoamer, and a silane coupling agent. The rheology modifier is bentonite, and its mass percentage in the primer base is 0.5–1.5%. The dispersant is BYK163 or BYK164, and its mass percentage in the primer base is 0.3–1.5%. The leveling agent is BYK354 or BYK361N, and its mass percentage in the primer base is 0.2–1%. The defoamer is BYK066N or BYKA530, and its mass percentage in the primer base is 0.1–1%. The silane coupling agent is KH560, and its mass percentage in the primer base is 0.4–1%.

[0015] Preferably, in the above-mentioned superhydrophobic coating, the fluorocarbon resin in the intermediate paint is tetrafluoropolymer, and the intermediate paint curing agent is aliphatic isocyanate.

[0016] Preferably, in the above-mentioned superhydrophobic coating, the intermediate paint pigment is rutile titanium dioxide, and the intermediate paint filler is one or more of barium sulfate, quartz powder, and polytetrafluoroethylene.

[0017] Preferably, in the above-mentioned superhydrophobic coating, the intermediate paint additive is one or more of the following: dispersant, leveling agent, defoamer, and silane coupling agent.

[0018] More preferably, the intermediate paint additives consist of a dispersant, a leveling agent, a defoamer, and a silane coupling agent. The dispersant is BYK111 or Deqian 912, and the mass percentage of the dispersant in the intermediate paint main agent is 0.3-1%. The leveling agent is BYK306 or Deqian 469, and the mass percentage of the leveling agent in the intermediate paint main agent is 0.5-1.5%. The defoamer is Deqian 6800 or BYK066N, and the mass percentage of the defoamer in the intermediate paint main agent is 0.1-0.5%. The silane coupling agent is KH560, and the mass percentage of the silane coupling agent in the intermediate paint main agent is 0.6-2%.

[0019] The present invention also provides a method for preparing the above-mentioned superhydrophobic coating, which includes the following steps:

[0020] First, mix the primer base agent and the primer hardener, and then apply them to the metal substrate by high-pressure airless spraying or brushing.

[0021] Mix the intermediate paint base agent and the intermediate paint hardener, and apply them to the dry primer layer by high-pressure airless spraying, air spraying or brushing.

[0022] The topcoat material is applied to the dried intermediate paint layer by high-pressure airless spraying or air spraying.

[0023] Preferably, in the above preparation method, the primer curing agent contains curing accelerator DMP-30, and the intermediate paint curing agent contains diluent ethyl acetate.

[0024] Preferably, in the above preparation method, the mass ratio of the primer main agent to the primer curing agent is 2.5:1 to 5:1.

[0025] Preferably, in the above preparation method, the primer is prepared by the following process: first, epoxy resin and butyl glycidyl ether are mixed at low speed (500 r / min to 700 r / min), then rheology modifier, primer pigment, and primer filler are added and dispersed at high speed (1800 r / min to 2100 r / min), and finally dispersant, leveling agent, defoamer, and silane coupling agent are added and dispersed at medium speed (1400 r / min to 1600 r / min). After the fineness is ≤80 μm, the mixture is filtered through a filter screen to obtain the primer.

[0026] Preferably, in the above preparation method, the intermediate paint main agent is prepared by the following process: tetrafluoropolymer, n-butanol, and ethyl acetate are mixed at low speed (500 r / min to 700 r / min), then intermediate paint pigments and fillers are added and dispersed at high speed (1800 r / min to 2100 r / min), and ground until the fineness is ≤35 μm. Finally, intermediate paint additives are added and dispersed at low speed (500 r / min to 700 r / min), and filtered through a filter screen to obtain the final product.

[0027] Preferably, in the above preparation method, the preparation method of the topcoat material is as follows: first, mix ethanol with fumed silica, heat to 50-60°C, stir at low speed (500r / min-700r / min) and keep warm for 10-15h.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] The superhydrophobic and oleophobic coating provided by this invention consists of a three-layer structure. The three layers work together as a whole to achieve their technical effects. There is a synergistic effect between the three layers, so that the entire coating can not only exert its excellent hydrophobic and oleophobic properties, but also has long-lasting anti-corrosion performance, extending the service life of the metal substrate, and improving the stability of the superhydrophobic and oleophobic coating.

[0030] The solvent-free anti-corrosion primer provided by this invention is a two-component, high-solids-content, environmentally friendly anti-corrosion coating. With a solids content of over 99%, this coating can significantly reduce VOC emissions, making it environmentally friendly and beneficial to construction workers. Furthermore, the epoxy resin in the coating has highly polar ether bonds and hydroxyl groups in its molecular structure, resulting in strong adhesion between the epoxy resin and the metal surface. The cashew oil-modified phenolic amine curing agent, with its unsaturated double-bonded carbon-15 long chain, produces a denser coating structure after cross-linking and curing with the epoxy resin. Additionally, the coating thickness can be designed to suit different corrosive environments, effectively shielding against moisture and salt spray, thus achieving long-lasting anti-corrosion performance.

[0031] The intermediate coating layer acts as a bridge connecting the primer and topcoat layers. Extensive experiments have shown that commonly used solvent-free anti-corrosion primers and superhydrophobic topcoats have poor compatibility. This is mainly because solvent-free anti-corrosion primers are epoxy systems, which are incompatible with the alcohols in superhydrophobic topcoats. Therefore, they cannot serve as carriers for superhydrophobic topcoats to construct micro-nano structures. In addition, the bisphenol A epoxy resin in solvent-free anti-corrosion primers contains aromatic ether bonds, which can easily penetrate the superhydrophobic topcoat under high ultraviolet sunlight. This causes the ether bonds in the solvent-free anti-corrosion primer to break and degrade, resulting in loss of gloss and chalking of the paint film. This further reduces the adhesion between the primer and the superhydrophobic topcoat, ultimately causing the superhydrophobic layer to lose its hydrophobic and oleophobic effects. This invention incorporates a superhydrophobic intermediate coating layer containing fluorocarbon resin. This intermediate coating layer has extremely short CF bonds with small atomic radii and bond energies as high as 451–485 KJ / mol. Its CF bonds are very stable, and outdoor high-UV sunlight has almost no effect on them, thus protecting the primer layer from the damage caused by high-UV sunlight. Furthermore, the intermediate coating layer is highly compatible with the superhydrophobic topcoat, which can effectively construct micro-nano structures on the surface of the intermediate coating layer, thereby achieving hydrophobic and oleophobic effects.

[0032] Compared to the commonly used super-double-hydrophobic two-layer coating structure on the market, the super-double-hydrophobic coating provided by this invention can extend the hydrophobic and oleophobic durability life from the conventional 3-5 years to 10-15 years, significantly improving the durability of existing super-double-hydrophobic coatings (two-layer structure). The different coatings in the super-double-hydrophobic coating of this invention are compatible with each other and work synergistically to exert long-lasting anti-corrosion and hydrophobic and oleophobic properties. It can adapt well to different corrosive environments, meet customers' needs for longer-term durability, and save customers significant costs. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the structure of the superhydrophobic coating combined with a solvent-free anti-corrosion primer provided by the present invention.

[0034] Figure 2 This is a schematic diagram of the superhydrophobic coating in Comparative Example 1. Detailed Implementation

[0035] The technical solution of the present invention will be clearly and completely described below with reference to embodiments. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0036] Unless otherwise specified, the methods described in the following examples are conventional; the reagents and materials described are commercially available unless otherwise specified.

[0037] Example 1

[0038] The structure of the superhydrophobic coating provided in this example is as follows: Figure 1 As shown, it includes a three-layer structure, from top to bottom: a topcoat layer, an intermediate coat layer, and a solvent-free anti-corrosion primer layer.

[0039] The primer layer consists of a primer base and a primer curing agent. The formula of the primer base is shown in Table 1, and its preparation process is as follows: First, epoxy resin bisphenol A type resin E51 and butyl glycidyl ether are added to the reaction vessel, and the mixing speed is reduced (500 r / min to 700 r / min) to mix evenly and disperse at low speed for 15 minutes; then, bentonite SD-2, titanium dioxide R902, iron oxide black 303T, barium sulfate, and quartz powder are added and dispersed at high speed (1800 r / min to 2100 r / min) for 30 minutes; finally, dispersant BYK163, leveling agent BYK354, defoamer BYK066N, and silane coupling agent KH560 are added and dispersed at medium speed (1400 r / min to 1600 r / min) for 30 minutes. The fineness is measured to be 80 microns. Finally, the mixture is filtered through a filter screen and packaged.

[0040] Table 1. Primer Main Agent Formulation

[0041] Element Percentage (quality ratio) Bisphenol A type resin E51 35.9％ Butyl glycidyl ether 7.5％ Titanium dioxide R902 19.7％ Iron Oxide Black 303T 9.1％ Barium sulfate 11.6％ Quartz powder 13.4％ Bentonite SD-2 0.8％ Dispersant BYK163 0.7％ Leveling agent BYK354 0.5％ Defoamer BYK066N 0.1％ Silane coupling agent KH560 0.7％

[0042] The primer curing agent is a cashew oil-modified phenolic amine curing agent, with the addition of curing accelerator DMP-30. Mixing the two in a specific ratio effectively improves the drying rate of the coating and shortens the recoating interval. In this example, the preparation process of the primer curing agent is as follows: the cashew oil-modified phenolic amine curing agent and DMP-30 are mixed evenly at a mass ratio of 98:2, dispersed at low speed (500 r / min to 700 r / min) for 30 minutes, filtered through a filter screen, and packaged.

[0043] The intermediate paint layer consists of an intermediate paint base agent and an intermediate paint curing agent. The formula of the intermediate paint base agent is shown in Table 2, and its preparation process is as follows: First, add tetrafluoroethylene resin HLR-670, n-butanol, and ethyl acetate to the reaction vessel, reduce the rotation speed (500 r / min to 700 r / min) and mix evenly, then disperse at low speed for 15 minutes; then add titanium dioxide R902, barium sulfate, quartz powder, and polytetrafluoroethylene, disperse at high speed (1800 r / min to 2100 r / min) for 30 minutes, then grind with a sand mill for 2 hours, measuring the fineness to 35 microns; finally, add dispersant BYK111, leveling agent BYK306, defoamer Deqian 6800, and silane coupling agent KH560, disperse at low speed (500 r / min to 700 r / min) for 30 minutes, filter with a filter screen, and package to obtain the final product.

[0044] Table 2 Formulation of Intermediate Paint Main Agent

[0045] Components Percentage (quality ratio) PTFE resin HLR-670 39.6％ n-Butanol 8.4％ Ethyl acetate 8.1％ Titanium dioxide R902 18.9％ Barium sulfate 12.1％ Quartz powder 6.3％ polytetrafluoroethylene 4.4％ Dispersant BYK111 0.5％ Leveling agent BYK306 0.5％ Defoamer Deqian 6800 0.3％ Silane coupling agent KH560 0.9％

[0046] The intermediate paint hardener is aliphatic isocyanate N3390, and ethyl acetate is added as a diluent. Mixing them in a specific ratio effectively improves the paint viscosity and increases its workability. In this example, the preparation process of the intermediate paint hardener is as follows: aliphatic isocyanate N3390 and ethyl acetate are mixed at a mass ratio of 80:20, dispersed at low speed (500 r / min to 700 r / min) for 30 minutes, filtered through a filter screen, and then packaged.

[0047] The raw materials for the topcoat layer consist of fumed silica, silane coupling agent KH560, and anhydrous ethanol. The specific formulation is shown in Table 3. The preparation method is as follows: First, anhydrous ethanol and fumed silica 974 are mixed and dispersed at a low speed (500 r / min to 700 r / min) for 15 minutes. Then, the mixture is heated to 50 to 60°C and kept at a low speed (500 r / min to 700 r / min) for 12 hours while stirring. Finally, silane coupling agent KH560 is added and the mixture is dispersed at a low speed (500 r / min to 700 r / min) for 3 hours to obtain the superhydrophobic topcoat.

[0048] Table 3 Topcoat Formula

[0049] Components Percentage (quality ratio) Fumed silica 974 10％ Silane coupling agent KH560 1％ ethanol 89％

[0050] Based on the primer, intermediate coat, and topcoat materials described above, this example prepares the coating through the following steps:

[0051] (1) After uniformly mixing the primer and primer curing agent at a mass ratio of 4.5:1, the mixture is uniformly applied to the metal substrate by high-pressure airless spraying.

[0052] (2) After uniformly mixing the intermediate paint base agent and intermediate paint curing agent at a mass ratio of 6:1, the paint is uniformly applied to the dried primer layer prepared in step (1) by brushing.

[0053] (3) Use topcoat material and apply it evenly to the dried intermediate paint layer by high-pressure airless spraying.

[0054] Comparative Example 1

[0055] Unlike Example 1, the superhydrophobic coating provided in this example has a two-layer structure, that is, it does not contain the intermediate paint layer in Example 1, but everything else is the same as in Example 1.

[0056] The coatings prepared in Example 1 and Comparative Example 1 were subjected to performance testing. The specific test items and results are shown in Table 4.

[0057] Table 4. Coating performance test results

[0058]

[0059]

[0060] The results above show that the superhydrophobic three-layer coating structure prepared by this invention outperforms the two-layer structure in Comparative Example 1 in all aspects, and significantly surpasses the commonly available superhydrophobic coating structures in terms of durability. Even in harsh environments with high salt spray and high UV radiation, the superhydrophobic coating of this invention maintains its excellent hydrophobic and oleophobic properties while also possessing long-lasting anti-corrosion performance. This is of great value in improving the corrosion resistance and durability of metal substrates, as well as their hydrophobic and oleophobic stability.

[0061] The above description is a preferred embodiment of the present invention and should not be construed as limiting the scope of the present invention. It should be noted that any modifications, equivalent substitutions, and improvements made by those skilled in the art within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A superhydrophobic coating combining a solvent-free anti-corrosion primer, characterized in that, The superhydrophobic coating layer comprises a solvent-free anti-corrosion primer layer, an intermediate paint layer, and a topcoat layer in sequence. The solvent-free anti-corrosion primer layer is composed of a primer base agent and a primer curing agent. The intermediate paint layer is composed of an intermediate paint base agent and an intermediate paint curing agent. The topcoat layer comprises fumed silica and ethanol. The primer is composed of 30-60% bisphenol A resin E51, 5-12% butyl glycidyl ether, 10-40% primer pigment, 10-40% primer filler, and 1.5-6% primer additives, by mass percentage; the primer curing agent is cashew oil modified phenolic amine curing agent. The intermediate paint main agent is composed of 30-50% tetrafluoropolymer, 10-20% diluent, 5-25% intermediate paint pigment, 5-25% intermediate paint filler, and 1.5-5% intermediate paint additives, by mass percentage, and the diluent is composed of n-butanol and ethyl acetate; the intermediate paint curing agent is an aliphatic isocyanate. The topcoat layer is composed of 3-15% fumed silica, 1-2% silane coupling agent, and 83-96% ethanol, by mass percentage; The primer pigment is rutile titanium dioxide and / or iron oxide black, and the primer filler is one or more of kaolin, talc, mica, barium sulfate, and feldspar. The primer additives consist of a rheology modifier, a dispersant, a leveling agent, a defoamer, and a silane coupling agent. The rheology modifier is bentonite, and its mass percentage in the primer base is 0.5-1.5%. The dispersant is BYK163 or BYK164, and its mass percentage in the primer base is 0.3-1.5%. The leveling agent is BYK354 or BYK361N, and its mass percentage in the primer base is 0.2-1%. The defoamer is BYK066N or BYKA530, and its mass percentage in the primer base is 0.1-1%. The silane coupling agent is KH560, and its mass percentage in the primer base is 0.4-1%. The intermediate paint pigment is rutile titanium dioxide, and the intermediate paint filler is one or more of barium sulfate, quartz powder, and polytetrafluoroethylene. The intermediate paint additives consist of a dispersant, a leveling agent, a defoamer, and a silane coupling agent. The dispersant is BYK111 or Deqian 912, and the mass percentage of the dispersant in the intermediate paint base is 0.3-1%. The leveling agent is BYK306 or Deqian 469, and the mass percentage of the leveling agent in the intermediate paint base is 0.5-1.5%. The defoamer is Deqian 6800 or BYK066N, and the mass percentage of the defoamer in the intermediate paint base is 0.1-0.5%. The silane coupling agent is KH560, and the mass percentage of the silane coupling agent in the intermediate paint base is 0.6-2%.

2. The method for preparing a superhydrophobic coating combined with a solvent-free anti-corrosion primer as described in claim 1, characterized in that, Includes the following steps: First, mix the primer base agent and the primer hardener, and then apply them to the metal substrate by high-pressure airless spraying or brushing. Mix the intermediate paint base agent and the intermediate paint hardener, and apply them to the dry primer layer by high-pressure airless spraying, air spraying or brushing. The topcoat material is applied to the dried intermediate paint layer by high-pressure airless spraying or air spraying.

3. The preparation method according to claim 2, characterized in that, The primer curing agent contains curing accelerator DMP-30, and the intermediate paint curing agent contains diluent ethyl acetate.

4. The preparation method according to claim 2, characterized in that, The mass ratio of the primer base agent to the primer curing agent is 2.5:1 to 5:1.

Images