A highly stable graphene-modified epoxy zinc-rich primer and its preparation method

Abstract

This invention discloses a highly stable graphene-modified epoxy zinc-rich primer and its preparation method, belonging to the field of heavy-duty anti-corrosion coating technology. The primer is a two-component system. Component A includes 15-25 parts epoxy resin, 30-60 parts zinc powder, 10-30 parts graphene ceramic powder, and an anti-settling synergistic system composed of hydrophobic fumed silica and organobentonite. The solvents are xylene and n-butanol (20-35 parts), and the additives are 0.4-8 parts. The key to its preparation lies in a specific sequential feeding process: first, organobentonite and fumed silica are rapidly dispersed using a portion of the resin and solvent to construct a macro- and micro-nested three-dimensional synergistic anti-settling network; then, graphene ceramic powder is added and fully dispersed; finally, zinc powder is added. This method effectively solves the problems of graphene dispersion and zinc powder sedimentation, resulting in a product with excellent storage stability, good anti-settling performance, and superior anti-corrosion properties.

Description

Technical Field

[0001] This invention relates to the field of heavy-duty anti-corrosion coatings, specifically to a highly stable graphene-modified epoxy zinc-rich primer and its preparation method. More specifically, it relates to a solvent-based graphene-modified epoxy zinc-rich primer with a zinc powder content between 30% and 60%, exhibiting excellent storage stability and anti-settling properties, and its preparation method. Background Technology

[0002] Epoxy zinc-rich primers are widely used in heavy-duty corrosion protection fields such as shipbuilding, bridges, and marine engineering due to their excellent cathodic protection and shielding performance. Traditional epoxy zinc-rich primers typically have a zinc powder content of over 60%, or even exceeding 80%. While the high zinc content provides good electrochemical protection, it also brings a series of problems: First, excessively high zinc powder density easily leads to severe sedimentation of the coating during storage, forming hard precipitates that require frequent stirring and affect application performance and the uniformity of the final paint film; second, high zinc powder content results in poor film density, high porosity, and insufficient physical shielding; third, the large amount of zinc oxide fumes generated during welding and cutting poses a health hazard.

[0003] To reduce zinc powder usage and improve overall performance, the industry has begun to explore the introduction of graphene. Graphene, with its unique two-dimensional sheet structure and excellent barrier and conductive properties, can significantly enhance the physical shielding effect of coatings and construct a conductive network, thereby maintaining or even improving corrosion resistance while reducing zinc powder usage. However, this technological approach faces two core challenges in practical applications:

[0004] The challenges of graphene dispersion and stabilization: Graphene has a large specific surface area and high surface energy, making it prone to agglomeration when pure graphene is added to resin systems. This not only prevents graphene from fully realizing its properties, but the graphene agglomerates themselves can also become defects. Adding graphene dispersions can also affect the performance of coatings.

[0005] Anti-settling challenges in low-to-medium zinc powder systems: Even when the zinc powder content is reduced to 30%–50%, sedimentation remains a significant issue. Single anti-settling agents struggle to provide long-term, effective suspension support in solvent-based systems with low to medium viscosity and high solids content.

[0006] Existing technologies have explored this area to some extent, but all have limitations. For example:

[0007] Patent CN113105800A discloses a graphene / carbon nanotube cold-coated zinc coating with a zinc powder content as high as 70-85 parts and uses an anti-settling agent. However, its system is acrylic resin and the zinc powder content is too high, failing to fundamentally solve the problems of sedimentation and environmental health.

[0008] In patent CN113831818A, the zinc powder content is 30-50%, and fumed silica and organic bentonite are used as anti-settling agents. However, it is an aqueous system, and its dispersion and anti-settling mechanisms are fundamentally different from those of solvent-based systems, so it cannot be directly applied.

[0009] Patent CN112961571A improves dispersibility by preparing graphene oxide / black talc composite materials, but it does not propose a specific solution for how to systematically solve the long-term anti-settling problem of composite systems with zinc powder and graphene coexisting at low to medium zinc content, especially in the range of 30% to 50%.

[0010] In conclusion, developing a solvent-based epoxy system with a zinc powder content of 30% to 60% that can simultaneously achieve efficient and stable dispersion of graphene and long-term anti-settling properties in coatings is of great significance for promoting the development of next-generation zinc-rich anti-corrosion coatings that are high-performance, low-consumption, and more environmentally friendly. Summary of the Invention

[0011] This invention aims to overcome the shortcomings of existing technologies and provide a solvent-based graphene-modified epoxy zinc-rich primer with good storage stability, excellent anti-settling performance, and outstanding anti-corrosion properties, as well as its preparation method. This invention effectively solves the common problems of graphene dispersion and coating sedimentation at low to medium zinc powder contents by constructing a "three-dimensional synergistic anti-settling network" and "graphene ceramic powder."

[0012] The objective of this invention is achieved through the following technical solution: a highly stable graphene-modified epoxy zinc-rich primer, which is a two-component coating comprising component A and component B; by mass parts, component A comprises: 15-25 parts epoxy resin, 30-60 parts zinc powder, 10-30 parts graphene ceramic powder, 1.5-3.5 parts anti-settling synergistic system, wherein the anti-settling synergistic system is composed of hydrophobic fumed silica and organobentonite, 20-35 parts solvent, and 0.4-8 parts additives.

[0013] In the aforementioned highly stable graphene-modified epoxy zinc-rich primer, the hydrophobic fumed silica in the anti-settling synergistic system is 0.5 to 1.5 parts, and the organic bentonite is 1.0 to 2.0 parts.

[0014] The solvent in the above-mentioned highly stable graphene-modified epoxy zinc-rich primer is at least one of xylene or butanol, and the solid content in group A is 40%~80%.

[0015] The zinc powder in the above-mentioned high-stability graphene-modified epoxy zinc-rich primer is a mixture of spherical zinc powder and flake zinc powder, with a mass ratio of spherical zinc powder to flake zinc powder of (1~4):1.

[0016] The solvent in the above-mentioned high-stability graphene-modified epoxy zinc-rich primer is a mixture of xylene and n-butanol, with a mass ratio of xylene to n-butanol of (3~4):1.

[0017] The above-mentioned highly stable graphene-modified epoxy zinc-rich primer contains 0.2 to 4 parts of dispersant, 0.1 to 2 parts of defoamer, and 0.1 to 2 parts of leveling agent in the additives.

[0018] The graphene added to the aforementioned high-stability graphene-modified epoxy zinc-rich primer is added by adding graphene ceramic powder, wherein 10 to 30 parts of graphene ceramic powder contain 0.1 to 2 parts of graphene.

[0019] The key to this invention lies in the construction of the three-dimensional synergistic anti-settling network, the specific preparation sequence, and the efficient and stable dispersion technology of graphene:

[0020] Three-dimensional synergistic anti-settling mechanism: Organic bentonite swells in the solvent to form a "house-like" macroscopic gel structure, providing basic thixotropy and suspending force; hydrophobic fumed silica forms a fine secondary network through hydrogen bonding between its nanoparticles. The combination of these two, with the macroscopic and microscopic networks interpenetrating and reinforcing each other, forms a three-dimensional spatial network that can strongly lock zinc powder particles, effectively resisting the settling of zinc powder due to gravity during storage.

[0021] The core preparation process, namely the preparation method of component A:

[0022] a. Pre-preparation of gel and slurry: Mix all the organic bentonite, epoxy resin, and solvent (xylene:n-butanol mass ratio of 4:1) according to the formula, and disperse at high speed by shearing until a uniform gel is formed. At the same time, pre-mix the functionalized graphene ceramic powder with a portion of the dispersant for later use.

[0023] b. Activate the anti-settling network: Under stirring, slowly add all the fumed silica to the gel from step a, increase the rotation speed to 1000-1500 rpm, and continue high-speed dispersion for 15-25 minutes to ensure that the fumed silica is fully dispersed and its thickening thixotropic properties are activated.

[0024] c. Introducing graphene: Reduce the rotation speed to medium (500-800 rpm), add the mixture of graphene ceramic powder and dispersion liquid, and disperse for 10-15 minutes to ensure that the graphene is evenly dispersed in the established anti-settling network.

[0025] d. Add zinc powder: While maintaining a medium-low stirring speed, slowly and evenly add all the zinc powder. After adding, increase the stirring speed to fully disperse the powder until the system is uniform and smooth, with no dry lumps.

[0026] e. Adjustment and completion: Add the remaining dispersant, defoamer, leveling agent and other additives, adjust the viscosity, stir evenly and filter to obtain component A.

[0027] This sequence ensures that the anti-settling network is fully constructed before the zinc powder is added, and disperses easily agglomerated graphene in the network structure before the zinc powder, maximizing the suspending ability of the anti-settling system and avoiding damage to the network from subsequent material additions.

[0028] Application of the above-mentioned highly stable graphene-modified epoxy zinc-rich primer in heavy-duty anti-corrosion coatings. Detailed Implementation

[0029] The present invention will be further described below through specific embodiments and comparative examples, but the present invention is not limited to these embodiments.

[0030] Examples 1-3 were set up to demonstrate three typical formulations (component A) with zinc powder contents of 30%, 36%, and 45%, respectively, as shown in Table 1.

[0031] The preparation method is as follows, which constructs a macro-micro nested three-dimensional collaborative anti-sinking network.

[0032] a. Pre-preparation of gel and slurry: Mix all the organic bentonite, epoxy resin, and solvent (xylene:n-butanol mass ratio of 4:1) according to the formula, and disperse at high speed by shearing until a uniform gel is formed. At the same time, pre-mix the functionalized graphene ceramic powder with a portion of the dispersant for later use.

[0033] b. Activate the anti-settling network: Under stirring, slowly add all the fumed silica to the gel from step a, increase the rotation speed to 1000-1500 rpm, and continue high-speed dispersion for 15-25 minutes to ensure that the fumed silica is fully dispersed and its thickening thixotropic properties are activated.

[0034] c. Introducing graphene: Reduce the rotation speed to medium (500-800 rpm), add the mixture of graphene ceramic powder and dispersion liquid, and disperse for 10-15 minutes to ensure that the graphene is evenly dispersed in the established anti-settling network.

[0035] d. Add zinc powder: While maintaining a medium-low stirring speed, slowly and evenly add all the zinc powder. After adding, increase the stirring speed to fully disperse the powder until the system is uniform and smooth, with no dry lumps.

[0036] e. Adjustment and completion: Add the remaining dispersant, defoamer, leveling agent and other additives, adjust the viscosity, stir evenly and filter to obtain component A.

[0037] Comparative Examples 1-3 were set up, all without hydrophobic fumed silica, with an increased proportion of organobentonite, and the preparation order was changed to all raw materials being added at once and dispersed at high speed. None of them constructed the macro-micro nested three-dimensional synergistic anti-settling network according to the method proposed in the above examples. Examples 1 and Comparative Examples 1, 2 and Comparative Examples 2, and 3 and Comparative Examples 3 had the same other components. Comparative Example 4 used the same raw materials as Example 1, but the preparation method was different; the raw materials were added sequentially, and the preparation method in Example 1 was not used. Comparative Example 5 did not add hydrophobic fumed silica, but the other components and preparation method were the same as in Example 1. Comparative Example 6 did not add organobentonite, but the other components and preparation method were the same as in Example 1. The specific compositions are shown in Table 1.

[0038] Table 1: Formulations (mass percentage) of Component A in Examples 1-3 and Comparative Examples 1-3

[0039]

[0040] The zinc powder is a mixture of spherical zinc powder and flake zinc powder, with a mass ratio of spherical zinc powder to flake zinc powder of (1~4):1.

[0041] Performance testing

[0042] The A components obtained in Examples 1-3 and Comparative Examples 1-6 were subjected to the following tests:

[0043] Sedimentation stability test: The sample was placed in a sealed container and stored in a 50°C constant temperature oven for 30 days (equivalent to about 6 months of room temperature storage). Afterwards, it was removed, cooled to room temperature, and the sedimentation status was evaluated. Standards: Grade 0 (no sedimentation) is excellent; Grade 1 (slight, soft sediment, easily stirred) is good; Grade 2 (medium-hard sediment, can be stirred) is average; Grade 3 (severe, hard sediment, difficult to stir) is poor.

[0044] Construction feasibility assessment: Apply the coating to the steel plate and observe the anti-sagging and film uniformity of the paint film.

[0045] Table 2: Test Results

[0046] The data in the table above shows that:

[0047] Settling stability: Examples 1 and 2 were both grade zero, with uniform paint in the can and no settling or stratification. Example 3 was grade one, with slight settling but easy to stir. Comparative Example 1 was grade two, and could be stirred. Comparative Examples 2 and 3 were grade three, with hard zinc powder precipitates forming at the bottom, making stirring difficult. The settling stability of Comparative Examples 1-3 was worse than that of their corresponding Examples 1-3, indicating that the macro-micro nested three-dimensional synergistic anti-settling network of Examples 1-3 has a significant effect. Comparative Example 4, because it did not follow the preparation method proposed in this invention, although the composition was exactly the same as Example 1, had worse settling stability than Example 1. Comparative Examples 5-6, because they lacked the three-dimensional synergistic anti-settling component, although the preparation method was exactly the same as Example 1, had worse settling stability than Example 1.

[0048] Workability: Examples 1-3 all exhibited good workability; the paint film did not drip when stationary and flowed easily after stirring. Comparative Examples 1-3, however, tended to drip and run during application, resulting in uneven paint films. The workability of Comparative Examples 4-6 was inferior to that of Example 1.

[0049] This invention successfully solves the long-term storage sedimentation problem of solvent-based graphene epoxy zinc-rich primers with zinc powder content of 20%~60% by constructing a synergistic anti-settling system with hydrophobic fumed silica and organobentonite, and by adopting a specific preparation sequence of "first building the network, then dispersing graphene, and finally adding zinc powder". The resulting product not only has excellent stability, but also fully utilizes the reinforcing effect of graphene, achieving excellent anti-corrosion performance while reducing the amount of zinc powder used. It is environmentally friendly, safe, and economical, and has broad prospects for industrial applications.

Claims

1. A highly stable graphene-modified epoxy zinc-rich primer, a two-component coating comprising component A and component B; characterized in that, By mass, component A comprises: 15-25 parts epoxy resin, 30-60 parts zinc powder, 10-30 parts graphene ceramic powder, 1.5-3.5 parts anti-settling synergistic system, wherein the anti-settling synergistic system is composed of hydrophobic fumed silica and organic bentonite, 20-35 parts solvent, and 0.4-8 parts additives.

2. The high-stability graphene-modified epoxy zinc-rich primer according to claim 1, characterized in that, In the aforementioned anti-settling synergistic system, the hydrophobic fumed silica comprises 0.5 to 1.5 parts, and the organic bentonite comprises 1.0 to 2.0 parts.

3. The high-stability graphene-modified epoxy zinc-rich primer according to claim 1, characterized in that, The solvent is at least one of xylene or butanol, and in group A, the solid content is 40% to 80%.

4. The high-stability graphene-modified epoxy zinc-rich primer according to claim 1, characterized in that, The zinc powder is a mixture of spherical zinc powder and flake zinc powder, with a mass ratio of spherical zinc powder to flake zinc powder of (1~4):

1.

5. The high-stability graphene-modified epoxy zinc-rich primer according to claim 1, characterized in that, The solvent is a mixture of xylene and n-butanol, with a mass ratio of xylene to n-butanol of (3~4):

1.

6. The high-stability graphene-modified epoxy zinc-rich primer according to claim 1, characterized in that, The additives contain 0.2 to 4 parts of dispersant, 0.1 to 2 parts of defoamer, and 0.1 to 2 parts of leveling agent.

7. The high-stability graphene-modified epoxy zinc-rich primer according to claim 1, characterized in that, The graphene added to the high-stability graphene-modified epoxy zinc-rich primer is added by adding graphene ceramic powder, wherein 10 to 30 parts of graphene ceramic powder contain 0.1 to 2 parts of graphene.

8. The high-stability graphene-modified epoxy zinc-rich primer according to any one of claims 1-6, characterized in that, The preparation of component A includes the following steps in sequence: a. Pre-gel preparation: Mix all the organic bentonite in the formula with epoxy resin and solvent, and disperse by high-speed shearing to form a uniform pre-gel; simultaneously, premix the functionalized graphene ceramic powder with a portion of the dispersant for later use. b. Constructing an anti-settling network: Under stirring, add the full amount of hydrophobic fumed silica to the pregel obtained in step a, and increase the rotation speed for high-speed dispersion for 15-25 minutes. c. Add graphene: Reduce the rotation speed to medium, add the amount of graphene ceramic powder specified in the formula, and disperse for 10-15 minutes; d. Add zinc powder: While stirring, slowly add the total amount of zinc powder in the formula. After adding, increase the speed to disperse until the system is uniform. e. Adjustment complete: Add the remaining dispersant, defoamer, leveling agent and other additives, adjust to the required viscosity, stir evenly and then filter and discharge.

9. The application of the high-stability graphene-modified epoxy zinc-rich primer according to any one of claims 1-7 in heavy-duty anti-corrosion coatings.

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