Waterborne epoxy coating as well as preparation method and application thereof

Abstract

The invention discloses a waterborne epoxy coating as well as a preparation method and application thereof, and relates to the technical field of coatings. The waterborne epoxy coating is prepared from a component A and a component B, the component A comprises waterborne epoxy resin, spherical zinc powder, flaky zinc powder, nano silicon dioxide and carbon nanotubes; the component B comprises a curing agent, a directional arrangement auxiliary agent and an anchoring auxiliary agent; the directional arrangement auxiliary agent is an auxiliary agent which has a directional arrangement effect on the carbon nano tube and the flaky zinc powder; the anchoring aid comprises a block copolymer and / or a star polymer. The waterborne epoxy coating has the advantages of being high in drying speed, high in water resistance and salt spray resistance, good in corrosion resistance, excellent in weather resistance and high in adhesive force, also has good welding resistance and cutting resistance, is suitable for the field of heavy corrosion prevention, and is particularly suitable for being used as workshop primer to be applied to the fields of containers, ships, steel structure bridges and petrochemical mechanical equipment.

Description

Technical Field

[0001] This invention relates to the field of coating technology, and in particular to a water-based epoxy coating, its preparation method, and its application. Background Technology

[0002] Solvent-based epoxy zinc-rich primers are widely used in heavy-duty corrosion protection fields such as containers, steel bridge structures, ships, and petrochemicals. However, solvent-based epoxy zinc-rich primers continuously release volatile organic compounds (VOCs) during the application and curing stages, failing to meet environmental protection requirements and exhibiting poor safety. In recent years, safe and environmentally friendly water-based epoxy zinc-rich primers have gradually replaced solvent-based ones. However, the drying speed of water-based epoxy zinc-rich primers is greatly affected by temperature and humidity, resulting in a slower drying rate. This limits their application in areas with high drying speed requirements, such as shop primers for containers, the inner surfaces of steel box girders, and epoxy zinc-rich primers used in winter.

[0003] Currently, the main methods to improve the drying speed of waterborne epoxy zinc-rich primers are to increase the reactivity of the curing agent or increase the amount of curing agent used. However, while these methods increase the drying speed, they reduce the anti-corrosion performance of the paint film, making it difficult to meet the requirements of heavy-duty anti-corrosion applications. Therefore, how to improve the drying speed of waterborne epoxy zinc-rich primers while ensuring anti-corrosion performance has become one of the key challenges that waterborne epoxy zinc-rich coatings need to address. Summary of the Invention

[0004] The present invention aims to at least solve one of the aforementioned technical problems existing in the prior art. Therefore, the object of the present invention is to provide a waterborne epoxy coating that incorporates nano-silica and carbon nanotubes, and is combined with directional alignment agents and anchoring agents to construct channels for water evaporation, thereby improving the drying speed of the waterborne epoxy coating while ensuring its anti-corrosion performance.

[0005] A second aspect of the present invention is to provide a method for preparing a waterborne epoxy coating.

[0006] A third aspect of the present invention is to provide an application of a waterborne epoxy coating.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A first aspect of the present invention provides a waterborne epoxy coating, wherein the raw materials for preparing the waterborne epoxy coating include component A and component B; component A includes waterborne epoxy resin, spherical zinc powder, flake zinc powder, nano-silica, and carbon nanotubes; and component B includes a curing agent, an orientation aligning agent, and an anchoring agent.

[0009] The orientation aligning agent is an agent that has an orientation aligning effect on carbon nanotubes and sheet-like zinc powder; the anchoring agent includes block copolymers and / or star polymers.

[0010] The waterborne epoxy coating of the present invention introduces nano-silica and carbon nanotubes, along with directional alignment aids and anchoring aids for anchoring structures, to control the arrangement and distribution of nano-silica and carbon nanotubes, thereby constructing channels for water evaporation, improving the drying speed of the waterborne epoxy coating, ensuring excellent anti-corrosion performance while drying rapidly, and enhancing the welding and cutting resistance of the coating film formed by the waterborne epoxy coating in conjunction with the reinforcing effect of other raw materials.

[0011] Furthermore, the present invention uses a combination of two zinc powders with different morphologies, namely spherical zinc powder and flake zinc powder, which is also beneficial to accelerate the drying speed of waterborne epoxy coatings. Compared with using a single type of zinc powder, the combination of flake zinc powder and spherical zinc powder can construct special channels, thereby increasing the solvent evaporation rate.

[0012] Preferably, the average particle size of the spherical zinc powder is ≥600 mesh.

[0013] More preferably, the average particle size of the spherical zinc powder is 600-1000 mesh.

[0014] More preferably, the average particle size of the spherical zinc powder is 700-900 mesh.

[0015] It should be noted that an average particle size of ≥600 mesh for spherical zinc powder means that it can pass through a 600-mesh sieve. For example, an average particle size of 800 mesh means that it can pass through an 800-mesh sieve.

[0016] Preferably, the average particle size of the flaky zinc powder is ≤20μm.

[0017] More preferably, the average particle size of the flake zinc powder is 10–20 μm.

[0018] More preferably, the average particle size of the flake zinc powder is 12–18 μm.

[0019] Preferably, the mass ratio of the spherical zinc powder to the flake zinc powder is 1:(0.05-15).

[0020] More preferably, the mass ratio of the spherical zinc powder to the flake zinc powder is 1:(0.5-11).

[0021] More preferably, the mass ratio of the spherical zinc powder to the flake zinc powder is 1:(0.5-1) or 1:(10-11).

[0022] Preferably, the average particle size of the nano-silica is 30–80 nm.

[0023] Preferably, the average diameter of the carbon nanotube is ≤100nm; the length of the carbon nanotube is ≥5μm.

[0024] More preferably, the average diameter of the carbon nanotube is 1–100 nm; the length of the carbon nanotube is 5–50 μm.

[0025] More preferably, the average diameter of the carbon nanotube is 10-20 nm; and the length of the carbon nanotube is 15-25 μm.

[0026] Preferably, the mass ratio of the nano-silica to the carbon nanotubes is 1:(0.1-10).

[0027] More preferably, the mass ratio of the nano-silica to the carbon nanotubes is 1:(0.5-5).

[0028] More preferably, the mass ratio of the nano-silica to the carbon nanotubes is 1:(2-5).

[0029] Preferably, the epoxy equivalent of the waterborne epoxy resin is 300-700 g / eq; and the solid content of the waterborne epoxy resin is ≥70%.

[0030] Preferably, component A comprises the following components in parts by mass:

[0031] 13-30 parts of waterborne epoxy resin, 5-60 parts of spherical zinc powder, 5-60 parts of flake zinc powder, 0.5-3.5 parts of nano-silica, and 0.5-5 parts of carbon nanotubes;

[0032] Component B comprises the following components in parts by mass:

[0033] 3-15 parts curing agent, 0.2-3 parts orientation alignment aid, and 0.3-3 parts anchoring aid.

[0034] Preferably, component A further comprises the following components by mass parts: 0.1 to 1 part of defoamer, 0.2 to 2 parts of dispersant, 5 to 35 parts of rust-preventive pigment, 0.1 to 1 part of anti-settling agent, and 1 to 10 parts of cosolvent;

[0035] Component B further includes the following components by mass: 0.1 to 2.5 parts of flash rust inhibitor and 1 to 10 parts of water.

[0036] More preferably, component A comprises the following components in parts by mass:

[0037] 14-20 parts of waterborne epoxy resin, 0.1-0.5 parts of defoamer, 0.2-0.8 parts of dispersant, 5-50 parts of spherical zinc powder, 10-60 parts of flake zinc powder, 5-10 parts of anti-rust pigment, 0.1-0.5 parts of anti-settling agent, 0.5-2 parts of nano-silica, 0.5-5 parts of carbon nanotubes, and 5-10 parts of co-solvent;

[0038] Component B comprises the following components in parts by mass:

[0039] 4-8 parts of water-based amine curing agent, 0.5-2 parts of orientation alignment aid, 0.5-2 parts of anchoring aid, 0.1-0.5 parts of flash rust inhibitor, and 1-5 parts of water.

[0040] More preferably, in component A, the spherical zinc powder has a mass fraction of 30-50 parts, and the flake zinc powder has a mass fraction of 10-30 parts.

[0041] Preferably, the defoamer includes at least one of silicone defoamer, polymer defoamer, and mineral oil defoamer.

[0042] Preferably, the dispersant is an aqueous dispersant, such as a polymeric dispersant.

[0043] Preferably, the anti-rust pigment includes at least one of zinc phosphate or its modified form, strontium phosphate, and iron phosphate powder.

[0044] Preferably, the anti-settling agent includes one or more of organobentonite, magnesium silicate, and polyamide wax.

[0045] Preferably, the co-solvent includes alcohols and / or alcohol ether solvents.

[0046] Preferably, the curing agent is a water-based amine curing agent; the water-based amine curing agent includes at least one of epoxy-modified amine, polyamide, and phenolic amine.

[0047] Preferably, the directional alignment aid includes a polymer copolymer emulsion, such as polyamide wax or nonionic modified ethylene-vinyl acetate copolymer wax.

[0048] Preferably, the anchoring agent comprises a copolymer obtained by controlled free radical polymerization, such as an acrylic copolymer or a polyether-modified acrylic copolymer. Specifically, the copolymer can be a front-end polymer, such as an acrylic block polymer.

[0049] Preferably, the flash rust inhibitor comprises an organic flash rust inhibitor.

[0050] Preferably, the mass ratio of component A to component B is (2-15):1.

[0051] More preferably, the mass ratio of component A to component B is (7-9):1.

[0052] A second aspect of the present invention provides a method for preparing the waterborne epoxy coating described in the first aspect of the present invention, comprising the following steps:

[0053] The raw materials of component A and component B are mixed separately, and then component A and component B are mixed to obtain water-based epoxy coating.

[0054] It should be noted that components A and B should not be mixed during storage; they should be mixed directly before use.

[0055] Preferably, the preparation method of the waterborne epoxy coating includes the following steps:

[0056] The cosolvent, dispersant, and waterborne epoxy resin are first stirred and mixed. Then, nano-silica and carbon nanotubes are added and stirred under the second stirring condition. Next, anti-settling agent and defoamer are added and mixed under the third stirring condition. Finally, spherical zinc powder, flake zinc powder and anti-rust pigment are added and stirred for the fourth time to obtain component A.

[0057] The water and orientation aligning agent are stirred for the fifth time, followed by the addition of curing agent, anchoring agent and flash rust inhibitor, and then stirred for the sixth time to obtain component B.

[0058] More preferably, the first stirring speed is 400-1000 r / min; the second stirring speed is 2000-3000 r / min; the third stirring speed is 1000-2000 r / min; the fourth stirring speed is 1000-2000 r / min; the fifth stirring speed is 1000-1500 r / min; and the sixth stirring speed is 600-1000 r / min.

[0059] More preferably, the first stirring time is 5-10 min; the second stirring time is 70-120 min; the third stirring time is 15-30 min; the fourth stirring time is 15-30 min; the fifth stirring time is 30-60 min; and the sixth stirring time is 20-40 min.

[0060] More preferably, during the preparation of component A, the temperature of the slurry system is maintained below 40°C by using condensate.

[0061] More preferably, the slurry fineness of component A is ≤40μm.

[0062] By adding and stirring the ingredients in stages, the components can be mixed more thoroughly and dispersed more evenly.

[0063] A third aspect of the present invention provides the application of the waterborne epoxy coating described in the first aspect of the present invention in the fields of containers, ships, bridges, petrochemicals, or machinery.

[0064] Specifically, the waterborne epoxy coating described in the first aspect of this invention is used as a shop primer in the fields of containers, ships, bridges or petrochemical machinery and equipment, and has excellent anti-corrosion performance, weather resistance and resistance to welding and cutting, and dries quickly.

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

[0066] The waterborne epoxy coating provided by this invention has the advantages of fast drying speed, strong water resistance and salt spray resistance, good anti-corrosion performance, excellent weather resistance, and high adhesion. At the same time, it also has good welding and cutting resistance. It solves the problems of slow drying speed of traditional waterborne zinc-rich epoxy coatings, especially slow drying under high humidity conditions, and the inability to balance fast drying and high anti-corrosion performance. It improves the drying speed while ensuring high anti-corrosion performance of waterborne epoxy coatings.

[0067] The waterborne epoxy coating of this invention has a drying time (touch dry) of up to 2.5 minutes, and its water resistance and salt spray resistance are both no less than 1000 hours. It balances drying speed and anti-corrosion performance, and also has excellent weather resistance and resistance to welding and cutting. Its weather resistance is no less than 8 months, making it suitable for heavy-duty anti-corrosion applications, especially as a shop primer for containers, ships, steel structure bridges, and petrochemical machinery equipment. Detailed Implementation

[0068] The present invention will be further described in detail below through specific embodiments. Unless otherwise specified, the raw materials, reagents, or apparatus used in the embodiments and comparative examples are all available from conventional commercial sources or can be obtained by existing technical methods. Unless otherwise specified, the test or experimental methods are conventional methods in the art.

[0069] Raw material description:

[0070] Waterborne epoxy resin: 6075, epoxy equivalent 400~600g / eq, solid content ≥70%, Honghui New Materials;

[0071] Defoamer: Organosilicon defoamer, 901W, Evonik Chemicals;

[0072] Dispersant: Polymer dispersant, 6208, Zhanxin;

[0073] Spherical zinc powder and flake zinc powder: Hunan Xinweiling, spherical zinc powder with an average particle size of 800 mesh, and flake zinc powder with an average particle size of 15μm;

[0074] Rust-preventive pigment: Phosphorus iron powder, general commercial use;

[0075] Anti-settling agent: Organic bentonite, SD-2, Hemings Chemical;

[0076] Nano-silica: hydrophobic, with an average particle size of 50nm, commonly used in commercial applications;

[0077] Carbon nanotubes: average diameter 15nm, average length 20μm, commonly used in commercial applications;

[0078] Cosolvent: Propylene glycol methyl ether, PM, Dow Chemical;

[0079] Water-based amine curing agent: epoxy-modified amine, with an effective ingredient content of 70% by mass, Westlake Chemicals;

[0080] Flash rust inhibitor: Organic flash rust inhibitor, H10, ASCOTEC;

[0081] Orientation aid: Nonionic modified ethylene-vinyl acetate copolymer wax, 8421, BYK Chemical;

[0082] Anchoring aid: Acrylic block polymer prepared by controlled free radical polymerization, 4585, BASF.

[0083] The following detailed description is provided in conjunction with specific embodiments and comparative examples.

[0084] Example 1

[0085] A water-based epoxy coating, the formulation of which is shown in Table 1, is prepared by the following steps:

[0086] The cosolvent, dispersant, and waterborne epoxy resin were placed in a clean reactor with circulating cooling water and stirred at 600 rpm for 10 min. Then, nano-silica and carbon nanotubes were added while stirring at 2000 rpm for 120 min. Next, anti-settling agent and defoamer were added sequentially, and the mixture was stirred at 2000 rpm for 20 min. Finally, spherical zinc powder, flake zinc powder, and rust-inhibiting pigment were added, and the mixture was stirred at 2000 rpm for another 20 min to obtain component A. Throughout the process, the slurry temperature was maintained below 40℃ using cooling water, resulting in a component A slurry with a fineness ≤40 μm.

[0087] After stirring deionized water and orientation accelerator at 1500 r / min for 60 min, add waterborne amine curing agent, anchoring agent and flash rust inhibitor, and stir at 1000 r / min for 20 min to obtain component B.

[0088] When using this water-based epoxy coating, simply mix component A with component B.

[0089] Examples 2-9

[0090] A water-based epoxy coating, the formulation of which is shown in Table 1, and the preparation method is the same as in Example 1.

[0091] Table 1. Formulation table of waterborne epoxy coatings for Examples 1-9 (parts by weight)

[0092]

[0093] Comparative Example 1

[0094] A water-based epoxy coating differs from Example 3 in that it uses an anti-rust pigment to replace nano-silica in equal amounts; otherwise, it is the same as Example 3.

[0095] Comparative Example 2

[0096] A water-based epoxy coating differs from Example 3 in that it uses an anti-rust pigment to replace carbon nanotubes in equal amounts; otherwise, it is the same as Example 3.

[0097] Comparative Example 3

[0098] A water-based epoxy coating differs from Example 3 in that it uses an anti-rust pigment to replace nano-silica and carbon nanotubes in equal amounts; otherwise, it is the same as Example 3.

[0099] Comparative Example 4

[0100] A waterborne epoxy coating differs from Example 3 in that it uses deionized water in equal amounts to replace the directional alignment agent and the anchoring agent; otherwise, it is the same as Example 3.

[0101] Comparative Example 5

[0102] A waterborne epoxy coating differs from Example 3 in that it uses commercially available hydrophobic micron-sized fumed silica (average particle size of 2 μm) in an equal amount to replace nano-silica; otherwise, it is the same as Example 3.

[0103] Comparative Example 6

[0104] Commercially available solvent-based epoxy zinc-rich coatings.

[0105] Comparative Example 7

[0106] Commercially available water-based epoxy zinc-rich coating products.

[0107] Performance testing

[0108] Unless otherwise specified, the paint film is formed as follows during the test: Component A and Component B in the above examples and comparative examples are mixed according to the actual mass ratio in the corresponding examples or comparative examples (i.e., Component A and Component B are directly mixed), diluted with water as needed for construction, sprayed onto carbon steel substrate, and dried at 25°C and 50% relative humidity.

[0109] The specific testing method is as follows:

[0110] Drying time (touch dry), weather resistance, welding and cutting were tested in accordance with GB / T 6747-2008;

[0111] Water resistance was tested in accordance with GB / T 1733-1993;

[0112] Early water resistance was tested after curing at 25℃ and 50% relative humidity for 24 hours, with a dry film thickness of 15-25μm, using cold-rolled steel sheet as the substrate;

[0113] Salt spray resistance and adhesion were tested in accordance with HG / T 3668-2020.

[0114] Except for the film thickness for drying time, which shall be in accordance with GB / T 6747-2008, the film thickness for other performance properties shall be in accordance with HG / T3668-2020.

[0115] The test results are shown in Tables 2 and 3.

[0116] Table 2 Performance test results of waterborne epoxy coatings in Examples 1-9

[0117] Example 1 2 3 4 5 6 7 8 9 Drying time / min 3 3 2.5 4 5 6 7 8 4 Weather resistance / month 8 12 15 12 12 12 12 12 13 Welding and Cutting qualified qualified qualified qualified qualified qualified qualified qualified qualified Salt spray resistance / h 1000 1500 2500 1800 1500 1500 1500 1500 2000 Adhesion / MPa 8.5 9 12 10.5 9 10 7 11 6 Water resistance / h 1000 1200 1500 1200 1200 1000 1100 1200 1200 Early water resistance No abnormalities No abnormalities No abnormalities No abnormalities No abnormalities No abnormalities No abnormalities No abnormalities No abnormalities

[0118] As can be seen from the test results in Table 2, the waterborne epoxy coating of this invention exhibits good drying speed, with a drying time not exceeding 8 minutes and a maximum of 2.5 minutes. It also demonstrates good water resistance and salt spray resistance, both exceeding 1000 hours, balancing drying speed and corrosion protection. Furthermore, it possesses excellent weather resistance and resistance to welding and cutting, with a weather resistance of at least 8 months and good adhesion of at least 6 MPa. Therefore, this waterborne epoxy coating ensures corrosion protection while improving drying speed, making it suitable for heavy-duty corrosion protection applications, such as as a primer for containers, ships, steel bridge structures, and petrochemical machinery.

[0119] Table 3 shows the performance test results of the coatings in Comparative Examples 1–7.

[0120]

[0121] Combining the test results in Tables 2 and 3, it can be seen that the coating in the comparative example shows a significant disadvantage compared with the water-based epoxy coating in the embodiments of the present invention in terms of balancing drying speed and anti-corrosion performance, especially in terms of significantly reduced water resistance. Compared with Example 3, Comparative Examples 1 and 2 omitted nano-silica or carbon nanotubes. In Comparative Example 1, the drying time increased to 10 minutes, and the water resistance was only 800 hours. In Comparative Example 2, the water resistance was also reduced, and it failed in terms of welding and cutting resistance. The performance of Comparative Examples 1 and 2 both declined. In Comparative Example 3, both nano-silica and carbon nanotubes were omitted, resulting in a further decrease in water resistance and drying speed. At the same time, the weather resistance, welding and cutting resistance were also poor, and the overall performance of the coating was reduced. In Comparative Example 4, the orientation and anchoring agents were omitted, making it difficult to build water evaporation channels, resulting in a longer drying time and even worse water resistance. In Comparative Example 5, fumed silica was used instead of nano-silica, and the water resistance was only 300 hours, which was only one-fifth of that in Example 3. In Comparative Example 6, a conventional commercially available solvent-based epoxy zinc-rich coating was used for testing. Although the drying time was short, the surface finish was not ideal in terms of weather resistance, salt spray resistance, adhesion, and water resistance.

[0122] In summary, the waterborne epoxy coating provided by this invention has the advantages of fast drying speed, strong water and salt spray resistance, good anti-corrosion performance, excellent weather resistance, and high adhesion. It also has good welding and cutting resistance, solving the problem of slow drying speed of traditional waterborne zinc-rich epoxy coatings, which cannot achieve both fast drying and high anti-corrosion performance. It is suitable for heavy-duty anti-corrosion fields, especially as a shop primer for containers, ships, steel structure bridges, and petrochemical machinery equipment.

[0123] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A water-based epoxy coating, characterized in that, The raw materials for preparing the waterborne epoxy coating include component A and component B; component A includes waterborne epoxy resin, spherical zinc powder, flake zinc powder, nano-silica, and carbon nanotubes; component B includes curing agent, orientation aid, and anchoring aid. The orientation aligning agent is an agent that has an orientation aligning effect on carbon nanotubes and sheet-like zinc powder; the anchoring agent includes block copolymers and / or star polymers.

2. The waterborne epoxy coating according to claim 1, characterized in that, The particle size of the spherical zinc powder is ≥600 mesh; And / or, the average particle size of the flake zinc powder is ≤20μm.

3. The waterborne epoxy coating according to claim 1 or 2, characterized in that, The mass ratio of the spherical zinc powder to the flake zinc powder is 1:(0.05-15).

4. The waterborne epoxy coating according to claim 1, characterized in that, The average particle size of the nano-silica is 30–80 nm. And / or, the average diameter of the carbon nanotube is ≤100nm; the length of the carbon nanotube is ≥5μm.

5. The waterborne epoxy coating according to claim 1 or 4, characterized in that, The mass ratio of the nano-silica to the carbon nanotubes is 1:(0.1~10).

6. The waterborne epoxy coating according to claim 1, characterized in that, Component A comprises the following components in parts by mass: 13-30 parts of waterborne epoxy resin, 5-60 parts of spherical zinc powder, 5-60 parts of flake zinc powder, 0.5-3.5 parts of nano-silica, and 0.5-5 parts of carbon nanotubes; Component B comprises the following components in parts by mass: 3-15 parts curing agent, 0.2-3 parts orientation alignment aid, and 0.3-3 parts anchoring aid.

7. The waterborne epoxy coating according to claim 6, characterized in that, Component A further includes the following components by mass: 0.1 to 1 part of defoamer, 0.2 to 2 parts of dispersant, 5 to 35 parts of rust-preventive pigment, 0.1 to 1 part of anti-settling agent, and 1 to 10 parts of cosolvent; Component B further includes the following components by mass: 0.1 to 2.5 parts of flash rust inhibitor and 1 to 10 parts of water.

8. The waterborne epoxy coating according to claim 7, characterized in that, The mass ratio of component A to component B is (2-15):

1.

9. A method for preparing the waterborne epoxy coating according to any one of claims 1 to 8, characterized in that, Includes the following steps: The raw materials of component A and component B are mixed separately, and then component A and component B are mixed to obtain water-based epoxy coating.

10. The application of the waterborne epoxy coating according to any one of claims 1 to 8 in the fields of containers, ships, bridges, petrochemicals or mechanical equipment.

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