Long-acting anticorrosive epoxy primer and preparation method thereof

Abstract

The invention relates to a long-acting anticorrosive epoxy primer and a preparation method thereof, and belongs to the technical field of protective coatings. The primer is a two-component system, a component A comprises epoxy resin and a thermal latent cationic initiator, and a component B comprises an amine curing agent and alkaline silane. The decomposition temperature of the initiator is designed to be matched with the exothermic peak of epoxy-amine curing reaction, and hydrolytic condensation of alkaline silane is triggered in the curing process, so that a compact composite structure is formed. According to the structure, the adhesive force, the shielding property and the medium permeability resistance of the coating are effectively improved, and the long-acting corrosion resistance of the coating is remarkably enhanced. The invention further provides a corresponding preparation method which is simple and controllable in process and suitable for protection of metal components in a harsh corrosion environment.

Description

Technical Field

[0001] This invention belongs to the field of protective coating technology, specifically relating to a long-lasting anti-corrosion epoxy primer suitable for corrosive environments and its preparation method. Background Technology

[0002] Epoxy primers, due to their excellent adhesion, chemical stability, and compatibility with the substrate, have become a key underlying material in anti-corrosion systems, and their anti-corrosion performance directly determines the protective effect of the entire coating system. Traditional epoxy primers mainly rely on the dense barrier formed after the epoxy resin cures to block corrosive media, and provide chemical passivation or electrochemical protection by adding rust-inhibiting pigments (such as zinc phosphate and zinc powder). However, the protective ability of such coatings is still insufficient when facing harsh environments such as marine chlorides and chemical atmospheres. Their cured network has microscopic defects, and during long-term service, microcracks are easily generated due to internal stress, aging, and other factors, leading to the penetration of corrosive media such as water, oxygen, and chloride ions, causing undercoat corrosion, and ultimately resulting in protective failure.

[0003] To further improve the shielding and durability of epoxy resin coatings, the industry has made numerous attempts. One important research direction is introducing inorganic phases into organic polymers to form hybrid materials. For example, simply physically mixing silane coupling agents into epoxy coatings aims to utilize their hydrolysis-condensation to enhance the coating. However, the hydrolysis-condensation reaction of silanes in epoxy-amine systems is prone to being out of sync with the curing reaction, leading to uneven dispersion of the inorganic phase and an imperfect hybrid network structure, which in turn affects the stability of the coating performance. Furthermore, conventional initiation systems struggle to precisely control the reaction timing of silanes, preventing the synergistic effect of the organic-inorganic phases from being fully realized.

[0004] Therefore, there is an urgent need in this field for a new technical solution that can more effectively and controllably construct a complete organic-inorganic hybrid structure inside the coating while maintaining the good workability and storage stability of epoxy coatings, thereby significantly improving its long-term anti-corrosion performance, especially adhesion, durability and resistance to media penetration. Summary of the Invention

[0005] The purpose of this invention is to provide a long-lasting anti-corrosion epoxy primer and its preparation method. By precisely controlling the curing process of the epoxy primer to form a dense hybrid network, its adhesion, shielding properties and long-term durability are significantly improved.

[0006] The objective of this invention can be achieved through the following technical solutions: In a first aspect, the present invention provides a long-lasting anti-corrosion epoxy primer, which is a two-component coating system composed of component A and component B: Component A comprises epoxy resin and a heat-latent cationic initiator; Component B contains an amine curing agent and an alkaline silane; The decomposition temperature of the thermally latent cationic initiator matches the exothermic peak of the epoxy-amine curing reaction, thereby triggering the hydrolysis and condensation of the basic silane during the curing process to form a dense organic-inorganic hybrid network structure.

[0007] As used in this text, "thermally latent cationic initiator" refers to an agent that is stable at room temperature but rapidly decomposes to produce cations (usually protons) upon reaching a specific trigger temperature (such as the curing exothermic peak in this system). This is a class of compounds. Its "latent" property is key to ensuring the storage stability of coatings and achieving precise timing control.

[0008] As used in this text, “composite cured material” refers to the final solid material formed by chemical cross-linking of “epoxy resin, amine curing agent and siloxane network generated from basic silane”.

[0009] Preferably, the thermally latent cationic initiator is a triarylthionium salt.

[0010] Preferably, the decomposition temperature of the triarylthionium salt is 60°C to 80°C.

[0011] Preferably, the basic silane is a silane coupling agent having an amino group.

[0012] Thus, the specific combination of triarylsulfonium salt (decomposition temperature 60-80°C) and aminosilane, together with the temperature-controlled dispersion process during preparation, ensures the product's storage stability and precise control of the curing process.

[0013] Preferably, the amino-containing silane coupling agent is (aminoethylaminopropyl)trimethoxysilane.

[0014] Preferably, the thermally latent cationic initiator has a mass content of 0.5% to 3% in component A, and the basic silane has a mass content of 1% to 5% in component B.

[0015] Preferably, the amine curing agent is a polyamide curing agent or a phenolic amine curing agent.

[0016] Preferably, component A further comprises a flake-shaped shielding pigment, wherein the flake-shaped shielding pigment is at least one of mica iron oxide and glass flakes.

[0017] In this way, the sheet-like shielding pigments are arranged in parallel overlapping patterns in the coating, which can greatly extend the penetration path of corrosive media and form a "macro-micro" dual physical barrier with the internal hybrid network, further enhancing the shielding effect.

[0018] Secondly, the present invention provides a method for preparing a long-lasting anti-corrosion epoxy primer, comprising the following steps: (1) Under the condition of maintaining the dispersion temperature below the decomposition temperature of the thermally latent cationic initiator, epoxy resin, thermally latent cationic initiator, flake-shaped shielding pigment, filler and additives are mixed to obtain component A:; (2) Component B is prepared by mixing an amine curing agent with an alkaline silane and a solvent; (3) Mix component A and component B to obtain the epoxy primer.

[0019] The beneficial effects of this invention are: (1) This invention achieves the regulation of the coating microstructure through a unique "time-sequential synergistic" curing mechanism. During the curing process, the initial epoxy-amine reaction not only constructs the basic polymer network, but the heat of reaction released also provides a precise trigger signal for subsequent hybridization reactions. When the system temperature reaches the decomposition threshold of the latent initiator, the generated acidic substances rapidly change the proton concentration of the local microenvironment, thereby activating the hydrolysis and condensation reaction of the basic silane. This stepwise chemical reaction process is conducive to the formation of a microscopic organic-inorganic composite structure.

[0020] (2) In this invention, the organic phase imparts the necessary flexibility and adhesion to the coating, while the inorganic phase provides excellent chemical stability and shielding performance. This composite structure can effectively prevent the penetration of corrosive media such as water molecules and chloride ions, while significantly improving the mechanical strength and aging resistance of the coating. Compared with simple physical blending systems, the resulting interpenetrating network has better structural uniformity and interfacial bonding. Detailed Implementation

[0021] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with embodiments, is provided below.

[0022] In the preparation of long-lasting anti-corrosion epoxy primers, although anti-rust pigments can provide basic physical shielding and chemical rust prevention, they also form microscopic penetration channels in the cured coating due to compatibility differences and interface defects with the epoxy resin matrix. These channels easily become preferential pathways for corrosive media penetration during long-term service, leading to the initiation and spread of corrosion under the coating and severely affecting the service life of the protective coating.

[0023] To address this problem, those skilled in the art typically focus on adjusting the components of the coating formulation, including but not limited to blending rust-inhibiting pigments, adding flake fillers to extend the penetration path, or modifying the resin system. However, while blending rust-inhibiting pigments aims to achieve better electrochemical or chemical passivation effects, it cannot fundamentally eliminate the inherent defects at the resin-pigment interface. Flake fillers extend the path through physical shielding, which can delay but not actively repair existing penetration channels; resin modification, while improving matrix toughness, may come at the cost of sacrificing chemical resistance and has limited effect on improving interfacial adhesion.

[0024] Through systematic research, the inventors discovered that the bottleneck in the long-term anti-corrosion performance of traditional coatings lies in the directional penetration of corrosive media along interfacial defects. Existing technologies only provide limited protection through physical barriers or passive passivation, failing to construct an active and durable interfacial barrier. To overcome this limitation, the inventors innovatively proposed a synergistic mechanism of "time-sequential synergistic curing coupled in-situ hybridization." By precisely controlling the reaction kinetics of the organic and inorganic phases, a dense composite structure is formed within the coating through self-assembly, fundamentally repairing microscopic defects at the interface and constructing an intelligent and efficient active protective barrier, thereby significantly improving the long-term anti-corrosion performance of the coating. This invention thus completes the creation of this invention.

[0025] All raw materials used in the examples and comparative examples are commercially available products, and unless otherwise specified, all amounts are parts by weight.

[0026] Example 1 A method for preparing a long-lasting anti-corrosion epoxy primer includes the following steps: (1) Preparation of component A: Add 50 parts of bisphenol A type epoxy resin (NPEL-128), 5 parts of n-butanol and 5 parts of xylene to a dispersion tank, and stir at 400 rpm for 5 minutes.

[0027] Add 0.5 parts of dispersant (BYK-163) and 0.3 parts of defoamer (BYK-066N), and stir for 5 minutes.

[0028] Add 15 parts of zinc phosphate and 10 parts of precipitated barium sulfate, increase the rotation speed to 1500 rpm, and disperse for 20 minutes until the fineness is ≤50μm.

[0029] Reduce the rotation speed to 600 rpm and slowly add 1.5 parts of a thermally latent cationic initiator, triarylthionium salt (e.g., SI-80L, decomposition temperature approximately 80°C), and disperse for 5 minutes.

[0030] Finally, add 0.5 parts of leveling agent (BYK-354) and 3 parts of xylene, stir slowly for 15 minutes, and discharge for later use. The temperature should be controlled below 50℃ throughout the dispersion process.

[0031] (2) Preparation of component B: In another container, mix 40 parts of polyamide curing agent (Cadele NX-2007), 3 parts of (aminoethylaminopropyl)trimethoxysilane and 7 parts of xylene, stir at 500 rpm for 10 minutes until homogeneous, discharge, seal and store for later use.

[0032] (3) Construction and curing: When using, mix component A and component B at a mass ratio of 5:1.

[0033] Differential scanning calorimetry (DSC) was performed on the mixture of components A and B in Example 1 of this case (heating rate 10°C / min). The exothermic peak of the epoxy-amine curing reaction was about 75°C, which matched well with the decomposition temperature (about 80°C) of the selected thermally latent cationic initiator.

[0034] Fourier transform infrared spectroscopy analysis was performed on the cured product of Example 1, and its spectrum was approximately... A broadened absorption peak appeared at the point, which can be attributed to the vibration of the Si-O-Si bond. This indicates that the basic silane successfully underwent hydrolysis and condensation reactions during the curing process. Combined with its significantly improved thermomechanical properties, it can be reasonably inferred that the in-situ formed siloxane structure effectively reinforces the epoxy resin matrix.

[0035] Example 2 A method for preparing a long-lasting anti-corrosion epoxy primer includes the following steps: (1) Preparation of component A: The steps are the same as in Example 1, but while adding precipitated barium sulfate, an additional 10 parts of mica iron oxide (Jinling Coatings, 800 mesh) and 5 parts of glass flakes (Changzhou Huabang, particle size 50-100μm) are added.

[0036] The amount of thermally latent cationic initiator added was adjusted to 2.0 parts.

[0037] (2) Preparation of component B: The steps are the same as in Example 1, but the amount of (aminoethylaminopropyl)trimethoxysilane added is adjusted to 4 parts.

[0038] (3) Construction and curing: Same as in Example 1.

[0039] Example 3 A method for preparing a long-lasting anti-corrosion epoxy primer includes the following steps: (1) Preparation of component A: The steps are the same as in Example 1, except that the amount of thermally latent cationic initiator added is adjusted to 0.8 parts.

[0040] (2) Preparation of component B: The steps are the same as in Example 1, but the amount of (aminoethylaminopropyl)trimethoxysilane added is adjusted to 1.5 parts.

[0041] (3) Construction and curing: When using, mix component A and component B at a mass ratio of 5:1.

[0042] Example 4 A method for preparing a long-lasting anti-corrosion epoxy primer includes the following steps: (1) Preparation of component A: The steps are the same as in Example 1, except that the amount of the thermally latent cationic initiator triarylthionium salt added is adjusted to 2.5 parts.

[0043] (2) Preparation of component B: Same as Example 1.

[0044] (3) Construction and curing: Same as Example 1.

[0045] Example 5 A method for preparing a long-lasting anti-corrosion epoxy primer includes the following steps: (1) Preparation of component A: Same as Example 1.

[0046] (2) Preparation of component B: In another container, mix 35 parts of phenolic amine curing agent (Cardley NX-545), 3 parts of (aminoethylaminopropyl)trimethoxysilane and 7 parts of xylene, stir at 500 rpm for 10 minutes until homogeneous, discharge, seal and store for later use.

[0047] (3) Construction and curing: When using, mix component A and component B at a mass ratio of 4.5:1.

[0048] Comparative Example 1 The preparation process is exactly the same as in Example 1, but no triaryl thioonium salt is added to component A and no basic silane is added to component B.

[0049] Comparative Example 2 The preparation process is exactly the same as in Example 1, but triarylthionium salt is not added to component A.

[0050] Comparative Example 3 The preparation process is exactly the same as in Example 1, but with one key modification: the (aminoethylaminopropyl)trimethoxysilane in component B is replaced with an equal amount of common acidic silane (γ-glycidoxypropyltrimethoxysilane, Nanjing Shuguang, KH-560).

[0051] Comparative Example 4 The preparation process is exactly the same as in Example 1, but with one key modification: an equal amount of bis-(4-tert-butylphenyl)iodonium hexafluorophosphate with a higher decomposition temperature (e.g., Yuanye Chemical, B21517, decomposition temperature >150°C) is used in component A.

[0052] Performance testing: 1. Basic mechanical property testing The adhesion test (GB / T 9286) uses the cross-cut test to assess the bond strength between the coating and the substrate. This method is a fundamental indicator for evaluating the protective durability of the coating. Impact resistance (GB / T 1732) determines the coating's resistance to mechanical impact through a drop hammer test, reflecting the coating's toughness under stress. Flexibility testing (GB / T 1731) uses the shaft bending test to examine the coating's ability to adapt to substrate deformation. These three tests together constitute the evaluation system for the mechanical integrity of the coating.

[0053] 2. Corrosion protection performance test Salt spray resistance (GB / T 1771) simulates harsh environments through accelerated neutral salt spray testing, focusing on the erosion propagation at scratches. This is a key indicator for evaluating the coating's protective durability. Cathodic disbondment resistance (GB / T 7790) specifically assesses the coating's durability under cathodic protection conditions. It examines the coating's stability in an electrochemical environment by measuring the disbondment radius. These two tests together verify the coating's long-term protective effect in corrosive environments.

[0054] 3. Accelerated Durability Testing The 70℃ water immersion adhesion test is an enhanced experiment based on the standard adhesion test. It examines the performance retention rate of the coating under extreme humid and hot conditions by accelerating the process with high-temperature water immersion. This test can effectively predict the interfacial stability of the coating during long-term use and is an important basis for evaluating the service life of the coating.

[0055] 4. Construction performance testing The pot life test determines the workable time window of the product by monitoring the viscosity change after the two-component system is mixed. Although this test does not directly reflect the final performance of the coating, it has important guiding significance for the practical application of the product and ensures the feasibility of the application process.

[0056] The coatings obtained from the above examples and comparative examples were subjected to performance tests according to standards, and the results are shown in the table below: All embodiments significantly outperformed the comparative examples in key corrosion resistance and durability indicators such as salt spray resistance (corrosion diffusion <3mm), cathodic disbondment resistance (disbondment radius <6mm), and retention of adhesion under humid heat. In particular, Example 2 exhibited the best overall performance.

[0057] Comparative Example 3 exhibited a short pot life (<1 hour) and large-area peeling, indicating that the method of directly mixing acidic silanes is not feasible. Comparative Example 4 (using a high decomposition temperature initiator) performed significantly worse than the embodiments of this invention, but similarly to Comparative Example 2, confirming that matching the initiator decomposition temperature with the curing exothermic peak is key to triggering hybridization. The comparative examples, in turn, validated the necessity and irreplaceability of each element in the technical solution.

[0058] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A long-lasting anti-corrosion epoxy primer, a two-component coating system, consisting of component A and component B, characterized in that: Component A comprises epoxy resin and a heat-latent cationic initiator; Component B contains an amine curing agent and an alkaline silane; The decomposition temperature of the thermally latent cationic initiator matches the exothermic peak of the epoxy-amine curing reaction, thereby triggering the hydrolysis and condensation of the basic silane during the curing process to obtain a composite cured product.

2. The long-lasting anti-corrosion epoxy primer according to claim 1, characterized in that, The thermally latent cationic initiator is a triarylthionium salt.

3. The long-lasting anti-corrosion epoxy primer according to claim 2, characterized in that, The decomposition temperature of the triarylthionium salt is 60°C to 80°C.

4. The long-lasting anti-corrosion epoxy primer according to claim 1, characterized in that, The basic silane is a silane coupling agent with an amino group.

5. The long-lasting anti-corrosion epoxy primer according to claim 4, characterized in that, The amino-containing silane coupling agent is (aminoethylaminopropyl)trimethoxysilane.

6. The long-lasting anti-corrosion epoxy primer according to claim 1, characterized in that, The thermally latent cationic initiator has a mass content of 0.5% to 3% in component A, and the basic silane has a mass content of 1% to 5% in component B.

7. The long-lasting anti-corrosion epoxy primer according to claim 1, characterized in that, The amine curing agent is a polyamide curing agent or a phenolic amine curing agent.

8. The long-lasting anti-corrosion epoxy primer according to claim 1, characterized in that, The A component also contains a flake-shaped shielding pigment, which is at least one of mica iron oxide and glass flakes.

9. A method for preparing the long-lasting anti-corrosion epoxy primer according to any one of claims 1-8, characterized in that, Includes the following steps: (1) Under the condition of maintaining the dispersion temperature below the decomposition temperature of the thermally latent cationic initiator, epoxy resin, thermally latent cationic initiator, flake-shaped shielding pigment, filler and additives are mixed to obtain component A:; (2) Component B is prepared by mixing an amine curing agent with an alkaline silane and a solvent; (3) Mix component A and component B to obtain the epoxy primer.

10. The application of the long-lasting anti-corrosion epoxy primer according to any one of claims 1 to 8 in the corrosion protection of metal components.

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