A cationic self-crosslinking core-shell structure metal anticorrosion emulsion, its preparation method and application

Abstract

This invention relates to a cationic self-crosslinking core-shell structure metal anti-corrosion emulsion, its preparation method, and its application, belonging to the interdisciplinary field of polymer chemistry and metal corrosion protection technology. This emulsion incorporates a benzimidazole structure into its molecular side chain. In preparing the emulsion, a cationic monomer with a benzimidazole structure, possessing both active corrosion inhibition and polymerizability, is first synthesized. This monomer is then used to synthesize a core-shell structured metal anti-corrosion emulsion. The synthesized cationic monomer contains various heteroatoms such as nitrogen and oxygen, enabling strong coordination and adsorption with the metal surface to form a dense protective layer. Simultaneously, the terminal polymerizable double bonds allow it to efficiently bond to the main chain of the polymer coating through free radical polymerization, achieving an integrated "anchoring-corrosion inhibition" function. The polymer coating synthesized with the participation of this monomer exhibits excellent adhesion, barrier properties, and active corrosion inhibition capabilities on the metal surface, significantly improving the long-term anti-corrosion performance of the coating under harsh environments.

Description

Technical Field

[0001] This invention relates to the interdisciplinary field of polymer chemistry and metal corrosion protection technology, and to a cationic self-crosslinking core-shell structure metal anticorrosion emulsion, its preparation method and application. Specifically, it relates to a method for first synthesizing a cationic monomer with a benzimidazole structure that has both active corrosion inhibition and polymerizability, and then using the monomer to synthesize a core-shell structure metal anticorrosion emulsion and its preparation method, which is particularly suitable for metal anticorrosion coatings. Background Technology

[0002] Metal corrosion is a major global problem, causing enormous economic losses and resource waste every year. Among numerous anti-corrosion technologies, organic coating protection is widely used due to its simple application, low cost, and significant effects. In water-based metal anti-corrosion coatings, the type of emulsion directly affects the coating's adhesion, corrosion resistance, and compatibility with the substrate. Compared to anionic emulsions, cationic emulsions have unique advantages: 1. Metal surfaces are usually negatively charged; cationic emulsions can actively adsorb onto the metal substrate due to electrostatic attraction, significantly improving initial adhesion; 2. During film formation, cationic emulsions can form an electrochemical passivation layer with the metal surface, inhibiting corrosion micro-cell reactions; 3. They have better penetration and conversion capabilities for residual trace rust on the metal surface.

[0003] However, existing cationic acrylate emulsions generally suffer from the following problems: first, the selection of cationic emulsifiers and functional monomers is limited, resulting in poor polymerization stability; second, insufficient crosslinking density leads to poor water resistance of the coating; and third, a lack of reactive groups that firmly bond with the metal surface makes it difficult to meet the requirements of harsh working conditions in the long term. To overcome these problems, "intelligent" anti-corrosion coatings have become a research hotspot. Among them, introducing molecules with active corrosion inhibition functions into the coating system is one of the effective strategies. Traditional corrosion inhibitors (such as chromates and phosphates) are effective, but they pose environmental pollution problems; while some small-molecule organic corrosion inhibitors (such as benzimidazole) are prone to seeping out and running off from the coating, resulting in a short protective life and potential contamination of the medium.

[0004] Therefore, developing a polymerizable corrosion inhibitor monomer that can be firmly fixed in the polymer network of a coating through chemical bonds to achieve durable and stable corrosion inhibition is of significant scientific and practical value. This type of monomer can interact with the metal surface through its corrosion-inhibiting groups and also participate in the polymerization reaction to become part of the coating, thus forming a stable and robust molecular protective layer at the coating / metal interface, providing continuous active protection even when the coating is damaged. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a cationic self-crosslinking core-shell structured metal anticorrosion emulsion, its preparation method, and its application. The method first synthesizes a cationic functional monomer with a benzimidazole structure that possesses both active corrosion inhibition and polymerizability. Then, using this monomer as both a corrosion inhibitor and a cationic functional monomer, a core-shell structured cationic anticorrosion emulsion is prepared via seed emulsion polymerization, providing a new solution for the development of metal surface protection technology.

[0006] The objective of this invention is achieved through the following technical solution: a cationic self-crosslinking core-shell structure metal anticorrosion emulsion, comprising the following components by weight: 45-80 parts methyl methacrylate, 25-45 parts butyl acrylate, 2-6 parts glycidyl methacrylate, 3-12 parts cationic special functional monomer Q, 1-5 parts diacetone acrylamide, 2-4 parts cationic emulsifier, 1-3 parts nonionic emulsifier, 0.3-1.0 parts initiator, 0.5-3 parts crosslinking agent, and 80-120 parts deionized water.

[0007] The structural formula of the cationic special functional monomer Q is shown in formula (I).

[0008] (I).

[0009] The above-mentioned cationic self-crosslinking core-shell structure metal anticorrosive emulsion is prepared by the following method for the cationic special functional monomer Q: dimethylaminoethyl methacrylate and 5-chloromethylbenzimidazole are mixed in an equimolar ratio, acetone solvent and hydroquinone polymerization inhibitor are added, and cationic special functional monomer Q containing polymeric double bonds and benzimidazole structure is obtained through nucleophilic substitution reaction.

[0010] The aforementioned cationic self-crosslinking core-shell structured metal corrosion-resistant emulsion undergoes a nucleophilic substitution reaction at 50-60°C for 10-15 hours.

[0011] The aforementioned cationic self-crosslinking core-shell structured metal corrosion-resistant emulsion uses one or both of hexadecyltrimethylammonium bromide and hexadecyltrimethylammonium chloride as the cationic emulsifier.

[0012] The aforementioned cationic self-crosslinking core-shell structure metal corrosion-resistant emulsion uses nonionic emulsifiers such as nonylphenol polyoxyethylene ether NP-10 and octylphenol polyoxyethylene ether OP-10, or both.

[0013] The aforementioned cationic self-crosslinking core-shell structured metal corrosion-resistant emulsion uses one or both of azobisisobutyramidine hydrochloride V-50 and azobisisobutyramidine imidazoline hydrochloride VA-044 as initiators.

[0014] The aforementioned cationic self-crosslinking core-shell structured metal anticorrosive emulsion uses adipic acid dihydrazide as the crosslinking agent.

[0015] A method for preparing the above-mentioned cationic self-crosslinking core-shell structured metal anticorrosion emulsion includes the following steps.

[0016] Step 1.

[0017] Core layer pre-emulsion: Mix 25-45 parts of methyl methacrylate, 15-25 parts of butyl acrylate, 2-6 parts of glycidyl methacrylate, 1.0-1.8 parts of cationic emulsifier, 0.5-1.5 parts of nonionic emulsifier and 40-50 parts of deionized water, and emulsify at high speed for 20 minutes.

[0018] Shell pre-emulsion: Mix 20-35 parts of methyl methacrylate, 10-20 parts of butyl acrylate, 3-12 parts of cationic special functional monomer Q, 1-5 parts of diacetone acrylamide, 0.8-1.6 parts of cationic emulsifier, 0.5-1.5 parts of nonionic emulsifier and 30-40 parts of deionized water, and emulsify at high speed for 20 minutes.

[0019] Step 2.

[0020] Seed emulsion and core layer polymerization: Add 10-30 parts of deionized water and 0.2-0.6 parts of cationic emulsifier to a reactor and heat to 80℃; add 1 / 4 of the core layer pre-emulsion and 1 / 3 of the initiator solution, and react for 30 minutes to form a seed emulsion; then add the remaining core layer pre-emulsion and 1 / 3 of the initiator solution dropwise, controlling the dropwise addition time to 1-1.5 hours, and keep warm for 1 hour to obtain the core layer emulsion.

[0021] Step 3.

[0022] Shell polymerization: Add shell pre-emulsion and remaining initiator dropwise to the core emulsion, controlling the dropwise addition time to 2-3 hours. After the dropwise addition is complete, heat to 85℃ and keep warm for 1 hour.

[0023] Step 4.

[0024] Post-processing: Cool to 40℃, add cross-linking agent, stir evenly, adjust pH to 5.0 with acetic acid, filter and discharge.

[0025] Application of the above-mentioned cationic self-crosslinking core-shell structured metal anti-corrosion emulsion in anti-corrosion coatings.

[0026] The advantages of this invention compared to the prior art are as follows.

[0027] 1. Enhanced Adhesion Through Cationic Electrostatic Adsorption: This invention introduces a quaternary ammonium salt structure into the shell layer, giving the latex particles a positive charge on their surface. When coated on a metal surface, the latex particles are electrostatically attracted to the negatively charged metal substrate, promoting rapid spreading and tight adhesion of the emulsion on the substrate surface, significantly improving both dry and wet adhesion.

[0028] 2. Dual Mechanisms Enhance Long-Term Corrosion Resistance: ① Because the corrosion-inhibiting component, benzimidazole, is covalently fixed in the coating, its corrosion inhibition effect is long-lasting and can effectively address localized damage to the coating, achieving "self-healing" active protection; ② The room-temperature self-crosslinking system of diacetone acrylamide and adipate dihydrazide further increases the crosslinking density. This dual synergistic effect effectively blocks the penetration of water, oxygen, and corrosive media.

[0029] 3. Synergistic effect of epoxy groups: Glycidyl methacrylate (GMA) is introduced into the core layer. Its epoxy groups can react with the amide groups of the shell layer or the hydroxyl groups on the metal surface after film formation, further enhancing the chemical bonding between the coating and the substrate and improving corrosion resistance and durability.

[0030] 4. Good polymerization stability: The use of a cationic / nonionic emulsifier compound system, combined with azobisisobutyramidine hydrochloride initiator, ensures the stability of the emulsion polymerization process, avoids gel formation, and the resulting emulsion has uniform particle size and excellent storage stability.

[0031] 5. Multifunctional and integrated: In addition to providing cationic properties, the quaternary ammonium salt groups also endow the coating with excellent antibacterial and antifungal properties, making it particularly suitable for metal protection in humid and hot environments. Detailed Implementation

[0032] The present invention will be further described in detail below with reference to embodiments, but is not limited thereto.

[0033] Unless otherwise stated, all raw materials used in the examples are commercially available industrial products.

[0034] Example 1: Cationic self-crosslinking core-shell structure metal anticorrosion emulsion.

[0035] 1. Synthesize cationic special functional monomer Q.

[0036] In a four-necked flask equipped with a stirrer, thermometer, and reflux condenser, 0.1 mol of dimethylaminoethyl methacrylate, 0.1 mol of 5-chloromethylbenzimidazole, 20 mL of acetone solvent, and 0.02 g of hydroquinone polymerization inhibitor were added. The mixture was heated to 55 °C and stirred for 12 hours. After the reaction was complete, the solvent and unreacted substances were removed by vacuum distillation to obtain a yellow, viscous liquid cationic functional monomer Q, with the following structural formula.

[0037] .

[0038] 2. Preparation of cationic preservative emulsion.

[0039] Core layer pre-emulsion: Mix 35 parts methyl methacrylate, 20 parts butyl acrylate, 4 parts glycidyl methacrylate, 1.5 parts cetyltrimethylammonium bromide, 1 part octylphenol polyoxyethylene ether (OP-10) and 40 parts deionized water, and emulsify at high speed for 20 minutes.

[0040] Shell pre-emulsion: Mix 28 parts methyl methacrylate, 15 parts butyl acrylate, 6 parts of the above-synthesized cationic special functional monomer Q, 3 parts diacetone acrylamide, 1.5 parts cetyltrimethylammonium bromide, 1 part OP-10 and 35 parts deionized water, and emulsify at high speed for 20 minutes.

[0041] 3. Seed emulsion polymerization.

[0042] Add the remaining 25 parts of deionized water and 0.5 parts of hexadecyltrimethylammonium bromide to the reactor, and heat to 80°C. Add 1 / 4 of the core layer pre-emulsion and 0.15 parts of the initiator azobisisobutyramidine hydrochloride (dissolved in 5 parts of water), and react for 30 minutes to form seeds.

[0043] 4. Shell polymerization.

[0044] Add the remaining core layer pre-emulsion and 0.15 parts of initiator azobisisobutyramidine hydrochloride (dissolved in 10 parts of water) dropwise over 1.5 hours, and keep warm for 1 hour to obtain the core layer emulsion.

[0045] Add shell pre-emulsion and 0.2 parts of initiator azobisisobutyramidine hydrochloride (dissolved in 10 parts of water) dropwise to the core emulsion over 2.5 hours, then heat to 85°C and keep warm for 1 hour.

[0046] 5. Post-processing.

[0047] Cool to 40℃, add 2 parts adipic acid dihydrazide, stir well, adjust pH to 5.0 with acetic acid, and filter through a 200-mesh filter.

[0048] Comparative Example 1 (Emulsion without cationic special functional monomer Q).

[0049] The difference from Example 1 is that monomer Q is not added during shell polymerization, but instead an equal amount of cationic monomer methacryloyloxyethyltrimethylammonium chloride (DMC) that does not contain benzimidazole structure.

[0050] Comparative Example 2 (conventional anionic emulsion).

[0051] An anionic emulsifier (sodium dodecyl sulfate) was used instead of the cationic emulsifier in Example 1. No other cationic monomers were added. The cationic monomers were replaced with an equal amount of methyl methacrylate. The rest of the formulation was the same as in Example 1.

[0052] Example 2: Performance Testing Section.

[0053] (a) Emulsion properties.

[0054] The main focus of this study is on the test methods for the appearance, viscosity, and storage stability of the cationic self-crosslinked core-shell structured metal anticorrosion emulsion of this invention, as follows.

[0055] 1. Appearance: Visual inspection.

[0056] 2. Emulsion viscosity: The viscosity of emulsions with a solid content of 45wt% was measured at 25℃ using an NDJ-1 rotational viscometer.

[0057] 3. Storage stability: Observe the changes in the emulsion after placing it in a 40℃ incubator for six months.

[0058] (ii) Coating performance.

[0059] 1. Sample preparation.

[0060] The emulsions of each embodiment and comparative example were sprayed onto degreased galvanized steel plates, with the film thickness controlled between 15 and 20 μm. After surface drying at room temperature, they were placed in an 80°C oven for 30 minutes to obtain the test samples.

[0061] 2. Testing methods.

[0062] Adhesion was tested according to GB / T 9286-1998.

[0063] Corrosion resistance was tested according to GB / T 10125-1997.

[0064] The resistance of the paint film to mold is determined according to GB / T 1741-2020 "Test Method for Resistance of Paint Film to Mold".

[0065] Solvent resistance was tested by vigorously wiping the prepared test sample surface 50 times with a cotton ball soaked in ethanol. The changes in the coating surface appearance were then visually assessed. Solvent resistance was graded into four levels: Level 1: no trace left after wiping; Level 2: only slight trace left after wiping; Level 3: slight trace left after wiping; Level 4: obvious trace left or the coating dissolved. Level 1 was the best, and Level 4 was the worst. The test results are shown in Table 1.

[0066] Table 1. Performance Comparison of Preservative Emulsions Prepared in Example 1, Comparative Example 1, and Comparative Example 2

[0067]

[0068] As shown in Table 1, the emulsion prepared by the method of this invention has moderate viscosity and good storage stability. After film formation, the emulsion exhibits excellent adhesion to the substrate, and the solvent resistance, mildew resistance, and especially the corrosion resistance of the coating are significantly improved. It can meet the performance requirements of emulsions for long-term metal corrosion protection and has broad application prospects.

[0069] 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 modifications, substitutions, or improvements based on the present invention are within the protection scope of the present invention.

Claims

1. A cationic self-crosslinking core-shell structure metal anticorrosion emulsion, characterized in that, The product comprises the following components by weight: 45-80 parts methyl methacrylate, 25-45 parts butyl acrylate, 2-6 parts glycidyl methacrylate, 3-12 parts cationic special functional monomer Q, 1-5 parts diacetone acrylamide, 2-4 parts cationic emulsifier, 1-3 parts nonionic emulsifier, 0.3-1.0 parts initiator, 0.5-3 parts crosslinking agent, and 80-120 parts deionized water. The structural formula of the cationic special functional monomer Q is shown in formula (I): （I）。 2. The cationic self-crosslinking core-shell structure metal anticorrosion emulsion according to claim 1, characterized in that, The preparation method of the cationic special functional monomer Q is as follows: dimethylaminoethyl methacrylate and 5-chloromethylbenzimidazole are mixed in an equimolar ratio, acetone solvent and hydroquinone polymerization inhibitor are added, and cationic special functional monomer Q containing polymeric double bonds and benzimidazole structure is obtained through nucleophilic substitution reaction.

3. The cationic self-crosslinking core-shell structure metal anticorrosion emulsion according to claim 2, characterized in that, The nucleophilic substitution reaction is carried out at 50-60°C for 10-15 hours.

4. The cationic self-crosslinking core-shell structure metal anticorrosion emulsion according to claim 1, characterized in that, The cationic emulsifier is one or both of hexadecyltrimethylammonium bromide and hexadecyltrimethylammonium chloride.

5. The cationic self-crosslinking core-shell structure metal anticorrosion emulsion according to claim 1, characterized in that, The nonionic emulsifier is one or both of nonylphenol polyoxyethylene ether NP-10 and octylphenol polyoxyethylene ether OP-10.

6. The cationic self-crosslinking core-shell structure metal anticorrosion emulsion according to claim 1, characterized in that, The initiator is one or both of azobisisobutyramidine hydrochloride V-50 and azobisisobutyramimidazole hydrochloride VA-044.

7. The cationic self-crosslinking core-shell structure metal anticorrosion emulsion according to claim 1, characterized in that, The crosslinking agent is adipic acid dihydrazide.

8. A method for preparing a cationic self-crosslinking core-shell structured metal anticorrosion emulsion according to any one of claims 1-7, characterized in that, Includes the following steps: Step 1: Core layer pre-emulsion: Mix 25-45 parts of methyl methacrylate, 15-25 parts of butyl acrylate, 2-6 parts of glycidyl methacrylate, 1.0-1.8 parts of cationic emulsifier, 0.5-1.5 parts of nonionic emulsifier and 40-50 parts of deionized water, and emulsify at high speed for 20 minutes; Shell pre-emulsion: Mix 20-35 parts of methyl methacrylate, 10-20 parts of butyl acrylate, 3-12 parts of cationic special functional monomer Q, 1-5 parts of diacetone acrylamide, 0.8-1.6 parts of cationic emulsifier, 0.5-1.5 parts of nonionic emulsifier and 30-40 parts of deionized water, and emulsify at high speed for 20 minutes; Step 2: Seed emulsion and core layer polymerization: Add 10-30 parts of deionized water and 0.2-0.6 parts of cationic emulsifier to a reactor, and heat to 80℃; add 1 / 4 of the core layer pre-emulsion and 1 / 3 of the initiator solution, and react for 30 minutes to form a seed emulsion; then add the remaining core layer pre-emulsion and 1 / 3 of the initiator solution dropwise, controlling the dropwise addition time to 1-1.5 hours, and keep warm for 1 hour to obtain the core layer emulsion; Step 3: Shell polymerization: Add shell pre-emulsion and remaining initiator dropwise to the core emulsion, control the dropwise addition time for 2-3 hours, and after the dropwise addition is completed, raise the temperature to 85℃ and keep it warm for 1 hour. Step 4: Post-processing: Cool to 40℃, add cross-linking agent, stir evenly, adjust pH to 5.0 with acetic acid, filter and discharge.

9. The application of a cationic self-crosslinking core-shell structured metal anti-corrosion emulsion according to any one of claims 1-7 in anti-corrosion coatings.

Images