A water-based anti-corrosion and environmentally friendly adhesive and its preparation method
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ANHUI DEPU POLYMER MATERIAL
- Filing Date
- 2026-06-03
- Publication Date
- 2026-06-30
Smart Images
Figure CN122302780A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of water-based adhesives, and more particularly to a water-based anti-corrosion and environmentally friendly adhesive and its preparation method. Background Technology
[0002] Adhesives are widely used in industrial fields. Currently, water-based adhesives face severe corrosion challenges in the protection of metal substrates. Water molecules easily penetrate the bonding interface, leading to metal oxidation and corrosion, thus significantly reducing bond strength and service life. To address this issue, existing technologies typically add corrosion inhibitors to the system.
[0003] A common approach is to introduce inorganic corrosion inhibitors such as chromates or molybdates. While these substances offer significant corrosion protection, they contain heavy metal ions, posing a significant threat to the environment and human health, and have been gradually phased out by the industry. Another approach involves using small-molecule organic corrosion inhibitors such as benzotriazole or mercaptobenzothiazole. Although these compounds provide some corrosion inhibition, their high polarity and poor compatibility with polymer resins lead to migration and precipitation over long-term storage, making it difficult to guarantee a lasting corrosion protection effect. Furthermore, some research has explored adding silane coupling agents to improve interfacial properties, such as aminosilanes or epoxysilanes. While single silane coupling agents can enhance adhesion, they lack highly efficient corrosion-inhibiting functional groups, limiting their protective capabilities in complex corrosive environments. Another approach involves introducing nanomaterials such as graphene oxide or nano-titanium dioxide. Although they offer good physical shielding, nanoparticles are prone to aggregation, leading to dispersion difficulties and significantly increasing system viscosity, affecting the adhesive's application performance. Therefore, developing a water-based adhesive that combines excellent corrosion protection with environmentally friendly properties is particularly urgent. Summary of the Invention
[0004] The purpose of this invention is to address the shortcomings of existing technologies by proposing a water-based anti-corrosion and environmentally friendly adhesive and its preparation method.
[0005] To achieve the above objectives, the present invention adopts the following technical solution: A water-based anti-corrosion and environmentally friendly adhesive comprises the following components in parts by weight: 30-50 parts of soft acrylic monomer, 20-40 parts of hard acrylic monomer, 0.5-10 parts of functional monomer, 2-8 parts of silane-imidazolium-pyrogallol acrylate monomer, 1-5 parts of emulsifier, 0.2-1.0 parts of initiator, 0.1-0.5 parts of pH buffer, 100-300 parts of deionized water, 0.5-2.0 parts of pH adjuster, 1-5 parts of film-forming aid, and 0.1-0.3 parts of defoamer;
[0006] The soft acrylic monomer is selected from at least one of butyl acrylate and ethylhexyl acrylate; the hard acrylic monomer is selected from at least one of methyl methacrylate and vinyl acetate; the functional monomer is selected from at least one of hydroxyethyl acrylate, hydroxybutyl acrylate, hydroxypropyl acrylate, and acrylamide; the emulsifier is fatty alcohol polyoxyethylene ether or a compound of fatty alcohol polyoxyethylene ether and anionic emulsifier; the initiator is selected from at least one of ammonium persulfate, potassium persulfate, and sodium persulfate and sodium bisulfite to form a redox initiation system, wherein the molar ratio of oxidizing initiator to reducing initiator is 1:(0.3-0.5); the pH buffer is at least one of sodium bicarbonate or sodium dihydrogen phosphate; the pH adjuster is ammonia; the film-forming aid is propylene glycol methyl ether acetate; and the defoamer is selected from at least one of organosilicon or mineral oil.
[0007] Preferably, the method for preparing the silane-imidazol-pyrogallol acrylate monomer includes the following steps: S1: Trimethylolpropane and pentaerythritol glycidyl ether were added to a drying reactor, along with anhydrous 1,4-dioxane and the catalyst tetrabutylammonium bromide. The mixture was stirred at room temperature for 30-40 minutes, then heated to 40-60°C and reacted for 4-8 hours. After removing the solvent and low-boiling-point substances by rotary evaporation, the mixture was vacuum dried at 40-60°C for 8-12 hours to obtain product 1 containing multiple hydroxyl groups. S2: Gallic acid, N,N'-dicyclohexylcarbodiimide (DCC), and 4-dimethylaminopyridine (DMAP) are added to a dry reactor. Anhydrous dichloromethane is added, and the mixture is stirred at 0-5℃ for 30-40 min. Anhydrous dichloromethane solution of product 1 is slowly added dropwise at a molar ratio of gallic acid to hydroxyl groups in product 1 of (0.3-0.5):1. After the addition is complete, the temperature is raised to 20-25℃ and the reaction is carried out for 8-10 h. After filtration, the filtrate is washed successively with 5-8% dilute hydrochloric acid, saturated sodium bicarbonate solution, and saturated brine. The organic phase is dried over anhydrous sodium sulfate and concentrated by rotary evaporation. Product 2 is obtained by silica gel column chromatography. S3: Add imidazole-4,5-dicarboxylic acid and anhydrous DMF to the reactor and stir to dissolve. Then add 1-hydroxybenzotriazole (HOBt) and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDCI) and stir to activate at room temperature for 30-40 min. Then add 3-aminopropyltriethoxysilane dropwise and stir to react at room temperature for 10-12 h. Pour the reaction solution into ice water and stir. Extract, combine the organic phases, and then wash and dry to obtain product 3. S4: Add product 3, DCC, and DMAP to a dry reactor, add anhydrous dichloromethane, stir at 0-5℃ for 30-40 min, add anhydrous dichloromethane solution of product 2 dropwise at a molar ratio of (0.4-0.6):1 of the remaining hydroxyl groups in product 3 to product 2, after which the temperature is raised to room temperature and reacted for 8-12 h, filter the filtrate and wash it 3-4 times with saturated brine, dry the organic phase with anhydrous sodium sulfate and concentrate it by rotary evaporation, and purify it by silica gel column chromatography to obtain product 4; S5: Dissolve product 4 in anhydrous dichloromethane, add hydroquinone, then add triethylamine, cool to 0-5℃, and slowly add an anhydrous dichloromethane solution of acryloyl chloride with a molar ratio of 1.0-1.1:1 to the remaining hydroxyl groups in product 4 at a molar ratio of 1.0-1.1:1. After the addition is complete, continue the reaction at 0-5℃ for 1-2 hours, then allow it to rise naturally to room temperature and stir for 3-4 hours. Filter to obtain the filtrate, wash it successively with dilute hydrochloric acid, saturated sodium bicarbonate solution, and saturated brine, dry the organic phase with anhydrous sodium sulfate, concentrate by rotary evaporation, purify by silica gel column chromatography, and dry under vacuum to obtain the silane-imidazolium-pyrogallol acrylate monomer.
[0008] Preferably, in step S1, the molar ratio of pentaerythritol glycidyl ether to trimethylolpropane is 1:(3.0-4.0).
[0009] Preferably, in step S2, the molar ratio of gallic acid, DCC, and DMAP is 1:(1.0-1.2):(0.05-0.1).
[0010] Preferably, in step S3, the molar ratio of imidazole-4,5-dicarboxylic acid to 3-aminopropyltriethoxysilane is 1:(0.9-1.0).
[0011] Preferably, in step S5, the mass fraction of the dilute hydrochloric acid is 5-8%.
[0012] Through the above technical solution, in step S1, under the action of the catalyst tetrabutylammonium bromide, the secondary hydroxyl group of trimethylolpropane attacks the epoxy group on pentaerythritol glycidyl ether, causing the epoxy ring to open and generating product 1. This step constructs a multi-armed star-shaped "backbone" rich in hydroxyl groups, providing a large number of reaction sites for subsequent multi-point esterification / amidation, and also helps to improve the hydrophilicity of the final molecule, making it more stable in the emulsion. In step S2, under the catalysis of DMAP, DCC reacts with the carboxyl group of gallic acid to generate an active ester intermediate. The hydroxyl group on product 1 nucleophilically attacks this intermediate to form an ester bond. The reaction byproduct is dicyclohexylurea, which can be removed by filtration to prepare product 2, thereby introducing the phenolic hydroxyl structure of gallic acid into the backbone. In step S3, the carboxyl group in the imidazole-4,5-dicarboxylic acid structure and the amino group in the 3-aminopropyltriethoxysilane structure undergo an amide condensation reaction under the action of HOBt and EDCI, thereby linking the imidazole group to the siloxane group to obtain product 3. In step S4, under the action of DCC and DMAP, the carboxyl group in the structure of product 3 undergoes an esterification reaction with the hydroxyl group in the structure of product 2, thereby grafting the "silane-imidazole" functional module onto the "gallic acid-backbone" structure to form product 4. At this point, the molecular structure simultaneously retains the polyphenolic hydroxyl group, imidazole ring, and triethoxysilane of gallic acid, as well as the unreacted terminal hydroxyl group. In step S5, the remaining hydroxyl group on product 4 acts as a nucleophile, attacking the acyl carbon atom of acryloyl chloride to generate an acrylate bond. Triethylamine is used to neutralize the HCl generated in the reaction, preventing acid catalysis from causing side reactions. Hydroquinone prevents acryloyl chloride or the product from undergoing self-polymerization under high temperature or light. The reaction is carried out at low temperature, which can reduce the thermal polymerization of acryloyl chloride / double bond and side reactions. This step introduces a carbon-carbon double bond, and finally prepares a silane-imidazol-pyrogallol acrylate monomer containing an aliphatic skeleton rich in hydroxyl groups, a gallic acid polyphenol structure, an imidazole group, a triethoxysilane, and a double bond structure.
[0013] A method for preparing a water-based anti-corrosion and environmentally friendly adhesive includes the following steps: Step 1: Preparation of pre-emulsion Solution A: Add some deionized water and emulsifier to the reaction vessel, stir evenly, then add soft acrylic acid monomer, hard acrylic acid monomer, and functional monomer, stir at high speed for 30-40 minutes to obtain Solution A, for later use. Solution B: Take another portion of deionized water and emulsifier, add silane-imidazol-pyrogallol acrylate monomer, stir at high speed for 20-30 minutes to obtain solution B, and set aside for later use; Step 2: Seed emulsion preparation Take 10-15% of the total amount of liquid A and add it to a four-necked flask equipped with a condenser and a stirrer. Heat the mixture to 70-80℃, add 1 / 3-1 / 2 of the formula amount of the oxidized initiator component and the reduced initiator component, and react for 15-30 minutes to obtain the seed emulsion. Step 3: Segmented polymerization and pH control Phase 1: Add the remaining solution A and the remaining oxidizing initiator components dropwise into a four-necked flask simultaneously, controlling the dropping rate to be completed within 1.5-2.0 hours, at a dropping temperature of 70-80℃; during this phase, control the pH of the system to 5.5-6.5 by adding a pH buffer. Phase 2: After the addition of solution A is completed, continue to add solution B, controlling the dropping rate to be completed within 1.0-1.5 hours, and maintaining the dropping temperature at 75-80℃; After the addition is complete, continue the reaction at 80-85℃ for 1.5-2 hours, then raise the temperature to 85-90℃ and hold for 20-30 minutes to reduce the residual monomer content. Step 4: Post-processing Cool the system from step three to below 40°C, add a pH adjuster to adjust the pH of the system to 7.0-8.0, then add a film-forming aid and a defoamer, stir at low speed for 15-20 minutes until the mixture is uniform, filter and discharge to obtain the water-based anti-corrosion and environmentally friendly adhesive.
[0014] Through the above technical solution, the silane-imidazol-pyrogallol acrylate monomer, due to the presence of acrylate double bonds, can undergo free radical copolymerization with soft / hard acrylic monomers and functional monomers during emulsion polymerization, thus becoming a component of the polymer chain's side chain. The gallic acid, imidazolium, and silane groups, originally in small molecule form, are transformed into oligomer side groups and will not migrate or precipitate to the adhesive surface over time, nor will they be washed away by water, thereby achieving long-lasting corrosion protection. The specific mechanism of action is as follows: 1. Corrosion inhibitory effect of pyrogallol group: The pyrogallol structure in the silane-imidazol-pyrogallol acrylate monomer structure can coordinate or adsorb with the metal surface through phenolic oxygen anions to form a dense organic inhibitory film; this film can hinder the anodic dissolution reaction and cathodic oxygen reduction reaction of the metal, thereby inhibiting metal corrosion. 2. Stabilizing and corrosion-inhibiting effect of imidazole ring: The imidazole ring is rigidly connected to the oligomer skeleton through amide bonds, which is equivalent to fixing the "corrosion-inhibiting active center" on the side group of the oligomer. This not only preserves its coordination ability with the metal surface, but also avoids its own migration and loss. 3. Synergistic effect of silane groups on adhesion enhancement and corrosion protection: During film formation and use, triethoxysilane groups can be hydrolyzed to generate silanols under the influence of trace amounts of moisture at wet interfaces or on metal surfaces. On the one hand, silanols can undergo condensation reactions with hydroxyl groups (M-OH) on the metal surface to generate Si-OM covalent bonds, significantly improving the adhesion between the adhesive layer and the metal substrate. At the same time, a dense siloxane network is formed at the interface to block the penetration of water and corrosive media. On the other hand, silanol molecules can undergo self-condensation to form cross-linked siloxane structures at the interface, further improving the cohesive strength and water resistance of the adhesive layer. 4. The auxiliary role of the polyhydroxy framework: The polyhydroxy framework enhances the polarity and hydrophilicity of molecules in the aqueous phase, which is conducive to their enrichment on the surface or interface region of emulsion particles, so that the anticorrosive functional groups are more distributed in the key region of "colloid-metal interface"; at the same time, the steric hindrance effect and hydrophilicity of the molecular framework can partially inhibit the premature self-condensation of silane groups in the aqueous phase, thus playing an auxiliary role in improving the stability of the emulsion.
[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention integrates the pyrogallol group, imidazole ring, silane group, and polymerizable double bond into a uniquely designed silane-imidazol-pyrogallol acrylate monomer. During emulsion polymerization, this monomer can copolymerize with acrylic monomers, allowing the anti-corrosion functional groups to be stably bonded to the polymer chain. This avoids the defects of traditional small molecule corrosion inhibitors, such as easy migration and loss. Moreover, the functional groups work synergistically to exert anti-corrosion effects, effectively improving the long-term anti-corrosion capability of the adhesive on the metal substrate.
[0016] 2. This invention uses a water-based formulation, does not add harmful heavy metal corrosion inhibitors such as chromates, has low volatile organic compound emissions, meets environmental protection regulations, and the raw materials and reaction process used are friendly to humans and the environment. It successfully solves the problem of insufficient environmental protection of traditional anti-corrosion adhesives and achieves a balance between anti-corrosion performance and environmental protection characteristics.
[0017] 3. This invention optimizes the component ratio and segmented polymerization process, ensuring a high conversion rate in the polymerization reaction, reducing monomer residue, and improving the mechanical and storage stability of the emulsion, while avoiding problems such as nanoparticle agglomeration. At the same time, silane groups can form covalent bonds with metal substrates, significantly enhancing the adhesion of the adhesive layer. Combined with the optimization of the polymer chain structure, the adhesive possesses excellent tensile shear strength, water resistance, and salt spray resistance, with stable construction performance, making it suitable for bonding and protecting metal substrates. Attached Figure Description
[0018] Figure 1 Product 3 obtained in Example 1 of this invention 1 H NMR spectrum. Detailed Implementation
[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with existing known technologies. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.
[0020] Example 1: I. Preparation of silane-imidazol-pyrogallol acrylate monomer: S1: Add 6.80 g of trimethylolpropane and 5.22 g of pentaerythritol glycidyl ether to a drying reactor, add 50 mL of anhydrous 1,4-dioxane, add 0.10 g of tetrabutylammonium bromide catalyst, stir at room temperature for 35 min, then heat to 50 °C and react for 6 h. After removing the solvent and low-boiling-point substances by rotary evaporation, dry under vacuum at 50 °C for 10 h to obtain product 1 containing polyhydroxyl groups; S2: Add 14.29 g gallic acid, 19.07 g DCC, and 0.82 g DMAP to a dry reactor, add 180 mL of anhydrous dichloromethane, stir at 2 °C for 35 min, slowly add 140 mL of anhydrous dichloromethane solution containing 12.02 g of product 1, and after the addition is complete, raise the temperature to 22 °C and react for 9 h. After filtration, wash the filtrate successively with 6% dilute hydrochloric acid, saturated sodium bicarbonate solution, and saturated brine. Dry the organic phase with anhydrous sodium sulfate and concentrate by rotary evaporation. Purify by silica gel column chromatography to obtain product 2. S3: 9.84 g imidazole-4,5-dicarboxylic acid and 60 mL anhydrous DMF were added to the reactor and stirred to dissolve. Then, 9.36 g HOBt and 13.29 g EDCI were added, and the mixture was stirred and activated at room temperature for 35 min. Next, 13.26 g 3-aminopropyltriethoxysilane was added dropwise, and the reaction was stirred at room temperature for 11 h. The reaction solution was poured into ice water and stirred for extraction. The organic phases were combined, washed, and dried to obtain product 3. A small amount of product 3 was analyzed by 1H NMR spectroscopy, and the results are as follows: Figure 1 As shown: δ8.15 (d, 1H) and 8.04 (s, 1H): The signal peaks in this region are attributed to aromatic protons on the imidazole ring, confirming the presence of the imidazole ring structure; δ3.82 (q, 6H): The signal peaks in this region are attributed to protons on the methylene (-OCH2-) group in the triethoxysilane group, confirming the introduction of the silane chain; δ1.21 (t, 9H): The signal peaks in this region are attributed to protons on the methyl (-CH3) group in the triethoxysilane group, confirming the presence of three ethoxy groups; δ3.26 (q δ1.72–1.62 (m, 2H): The signal peak in this region is attributed to the proton on the methylene group (-N-CH2-) adjacent to the nitrogen atom of the amide. The low chemical shift is due to the attachment of an electronegative nitrogen atom, confirming the formation of an amide bond; δ1.72–1.62 (m, 2H): The signal peak in this region is attributed to the proton on the methylene group in the middle of the propyl chain; δ0.68 (t, 2H): The signal peak in this region is attributed to the proton on the methylene group (Si-CH-) attached to the silicon atom, confirming the presence of the silane coupling agent linker arm; 1 The peak positions, peak shapes, and integrals of the H NMR spectrum correspond one-to-one with the hydrogen atom environments of the target compound (product 3), verifying the correctness of the compound structure.
[0021] S4: Add 13.26g of product 3, 14.30g of DCC, and 0.62g of DMAP to a dry reactor, add 140mL of anhydrous dichloromethane, stir at 2℃ for 35min, add dropwise anhydrous dichloromethane solution containing 24.8g of product 2, and after the addition is complete, heat to room temperature and react for 10h. Filter the filtrate and wash it 3 times with saturated brine. Dry the organic phase with anhydrous sodium sulfate and concentrate by rotary evaporation. Purify by silica gel column chromatography to obtain product 4. S5: Dissolve 24.62 g of product 4 in 250 mL of anhydrous dichloromethane, add 0.01 g of hydroquinone, then add 11.06 mL of triethylamine, cool to 2 °C, and slowly add 44.2 mL of anhydrous dichloromethane solution of acryloyl chloride with a molar concentration of 1.5 mol / L. After the addition is complete, continue the reaction at 2 °C for 1.5 h, then allow it to rise naturally to room temperature and stir for another 3.4 h. Filter to obtain the filtrate, wash successively with dilute hydrochloric acid, saturated sodium bicarbonate solution, and saturated brine, dry the organic phase with anhydrous sodium sulfate, concentrate by rotary evaporation, purify by silica gel column chromatography, and dry under vacuum to obtain silane-imidazolium-pyrogallol acrylate monomer.
[0022] The hydroxyl values of products 1, 2, 4, and the silane-imidazol-pyrogallol acrylate monomer were determined by phthalic anhydride esterification method. The results were calculated according to the formula: Hydroxyl value (mg KOH / g) = [(V0-V1)×C×56.1] / m; V0 is the volume of sodium hydroxide solution consumed by the blank sample; V1 is the volume of sodium hydroxide solution in the sample; C is the molar concentration of sodium hydroxide solution; m is the sample mass. The results showed that the hydroxyl value of product 1 was 895±3 mg KOH / g, confirming the successful formation of the polyhydroxy backbone; the hydroxyl value of product 2 was 454±2 mg KOH / g, verifying that gallic acid was successfully attached to product 1 through esterification, and the hydroxyl group was effectively consumed; the hydroxyl value of product 4 was 344±2 mg KOH / g, indicating that the "silane-imidazolium" module was successfully grafted onto the "gallic acid-backbone"; the hydroxyl value of the silane-imidazolium-pyrogallol acrylate monomer was 134±1 mg KOH / g, confirming the successful introduction of the acrylate double bond, and confirming that each step of the reaction proceeded as expected and the target molecule structure was accurate.
[0023] II. Preparation of water-based anti-corrosion and environmentally friendly adhesives: Formula: 30g butyl acrylate, 20g methyl methacrylate, 0.5g hydroxyethyl acrylate, 2g silane-imidazolium-pyrogallol acrylate monomer, 1g fatty alcohol polyoxyethylene ether, 0.2g initiator (ammonium persulfate and sodium bisulfite in a molar ratio of 1:0.3), 0.1g sodium bicarbonate, 100g deionized water, 0.5g ammonia (25% by mass), 1g propylene glycol methyl ether acetate, 0.1g defoamer (a mixture of mineral oil and hydrophobic silica); Step 1: Preparation of pre-emulsion Solution A: Add some deionized water and emulsifier to the reaction vessel, stir evenly, then add butyl acrylate, methyl methacrylate and hydroxyethyl acrylate, stir at high speed for 30 minutes to obtain solution A, for later use; Solution B: Take another portion of deionized water and fatty alcohol polyoxyethylene ether, add the silane-imidazol-pyrogallol acrylate monomer, stir at high speed for 20 min to obtain solution B, and set aside. Step 2: Seed emulsion preparation Take 10% of the total amount of liquid A and add it to a four-necked flask equipped with a condenser and a stirrer. Heat the mixture to 70°C, add 1 / 3 of the formula amount of ammonium persulfate initiator component and sodium bisulfite initiator component, and react for 15 minutes to obtain seed emulsion. Step 3: Segmented polymerization and pH control Phase 1: The remaining solution A and the remaining ammonium persulfate initiator components are simultaneously added dropwise to a four-necked flask, with the dropping rate controlled to be completed within 1.5 hours and the dropping temperature at 70°C; during this phase, the pH of the system is controlled to be 5.5 by adding sodium bicarbonate. Phase 2: After the addition of solution A is completed, continue to add solution B, controlling the dropping rate to be completed within 1.0 hour, and maintaining the dropping temperature at 75℃; After the addition is complete, continue the reaction at 80℃ for 1.5 hours, then raise the temperature to 85℃ and hold for 20 minutes to reduce the residual monomer content. Step 4: Post-processing Cool the system from step three to below 40°C, add a pH adjuster to adjust the pH of the system to 7.0, then add propylene glycol methyl ether acetate and defoamer, stir at low speed for 15 minutes until the mixture is uniform, filter and discharge to obtain the water-based anti-corrosion and environmentally friendly adhesive.
[0024] Example 2: Preparation of water-based anti-corrosion and environmentally friendly adhesive: Formula: 35g butyl acrylate, 25g methyl methacrylate, 5.0g hydroxyethyl acrylate, 7g silane-imidazolium-pyrogallol acrylate monomer, 2g fatty alcohol polyoxyethylene ether, 0.3g initiator (ammonium persulfate and sodium bisulfite in a molar ratio of 1:0.4), 0.3g sodium bicarbonate, 200g deionized water, 1.2g ammonia (25% by mass), 3g propylene glycol methyl ether acetate, 0.2g defoamer (a mixture of mineral oil and hydrophobic silica); Step 1: Preparation of pre-emulsion Solution A: Add some deionized water and emulsifier to the reaction vessel, stir evenly, then add butyl acrylate, methyl methacrylate and hydroxyethyl acrylate, stir at high speed for 35 minutes to obtain solution A, for later use; Solution B: Take another portion of deionized water and fatty alcohol polyoxyethylene ether, add the silane-imidazol-pyrogallol acrylate monomer, stir at high speed for 25 min to obtain solution B, and set aside. Step 2: Seed emulsion preparation Take 12% of the total amount of liquid A and add it to a four-necked flask equipped with a condenser and a stirrer. Heat the mixture to 75°C, add 1 / 3 of the formula amount of ammonium persulfate initiator component and sodium bisulfite initiator component, and react for 20 minutes to obtain seed emulsion. Step 3: Segmented polymerization and pH control Phase 1: The remaining solution A and the remaining ammonium persulfate initiator components are simultaneously added dropwise to a four-necked flask, with the dropping rate controlled to be completed within 1.6 hours and the dropping temperature at 75°C; during this phase, the pH of the system is controlled to be 6.0 by adding sodium bicarbonate. Phase 2: After the addition of solution A is completed, continue to add solution B, controlling the dropping rate to complete the addition within 1.2 hours, and maintaining the dropping temperature at 78℃; After the addition was completed, the reaction was continued at 82℃ for 1.6 hours, and then the temperature was raised to 87℃ and held for 25 minutes to reduce the residual monomer content. Step 4: Post-processing Cool the system from step three to below 40°C, add a pH adjuster to adjust the pH of the system to 7.5, then add propylene glycol methyl ether acetate and defoamer, stir at low speed for 18 minutes until the mixture is uniform, filter and discharge to obtain the water-based anti-corrosion and environmentally friendly adhesive.
[0025] The preparation method of the silane-imidazol-pyrogallol acrylate monomer is the same as in Example 1.
[0026] Example 3: Preparation of water-based anti-corrosion and environmentally friendly adhesive: Formula: 50g butyl acrylate, 40g methyl methacrylate, 10g hydroxyethyl acrylate, 8g silane-imidazolium-pyrogallol acrylate monomer, 5g fatty alcohol polyoxyethylene ether, 1.0g initiator (ammonium persulfate and sodium bisulfite in a molar ratio of 1:0.5), 0.5g sodium bicarbonate, 300g deionized water, 2.0g ammonia (25% by mass), 5g propylene glycol methyl ether acetate, 0.3g defoamer (a mixture of mineral oil and hydrophobic silica); Step 1: Preparation of pre-emulsion Solution A: Add some deionized water and emulsifier to the reaction vessel, stir evenly, then add butyl acrylate, methyl methacrylate and hydroxyethyl acrylate, stir at high speed for 40 minutes to obtain solution A, for later use; Solution B: Take another portion of deionized water and fatty alcohol polyoxyethylene ether, add the silane-imidazol-pyrogallol acrylate monomer, stir at high speed for 30 min to obtain solution B, and set aside. Step 2: Seed emulsion preparation Take 15% of the total amount of liquid A and add it to a four-necked flask equipped with a condenser and a stirrer. Heat the mixture to 80°C, add half of the formula amount of ammonium persulfate initiator component and sodium bisulfite initiator component, and react for 30 minutes to obtain seed emulsion. Step 3: Segmented polymerization and pH control Phase 1: The remaining solution A and the remaining ammonium persulfate initiator components are simultaneously added dropwise to a four-necked flask, with the dropping rate controlled to be completed within 2.0 hours and the dropping temperature at 80℃; during this phase, the pH of the system is controlled to be 6.5 by adding sodium bicarbonate. Phase 2: After the addition of solution A is completed, continue to add solution B, controlling the dropping rate to be completed within 1.5 hours, and maintaining the dropping temperature at 80℃; After the addition is complete, continue the reaction at 85℃ for 2 hours, then raise the temperature to 90℃ and keep it at that temperature for 30 minutes to reduce the residual monomer content. Step 4: Post-processing Cool the system from step three to below 40°C, add a pH adjuster to adjust the pH of the system to 8.0, then add propylene glycol methyl ether acetate and defoamer, stir at low speed for 20 minutes until the mixture is uniform, filter and discharge to obtain the water-based anti-corrosion and environmentally friendly adhesive.
[0027] The preparation method of the silane-imidazol-pyrogallol acrylate monomer is the same as in Example 1.
[0028] Comparative Example 1: Based on Example 2, the difference is that an equal amount of Product 2 was used to replace the silane-imidazol-pyrogallol acrylate monomer in the formulation to prepare the adhesive, and the rest is the same as in Example 2.
[0029] Comparative Example 2: Based on Example 2, the difference is that an equal amount of product 3 was used to replace the silane-imidazol-pyrogallol acrylate monomer in the formulation to prepare the adhesive, and the rest is the same as in Example 2.
[0030] Comparative Example 3: Based on Example 2, the difference is that an equal amount of product 4 was used to replace the silane-imidazol-pyrogallol acrylate monomer in the formulation to prepare the adhesive, and the rest is the same as in Example 2.
[0031] Comparative Example 4: Based on Example 2, the difference is that the silane-imidazol-pyrogallol acrylate monomer is removed from the formulation, and the rest is the same as in Example 2.
[0032] Comparative Example 5: Based on Example 2, the difference is that the silane-imidazolium-pyrogallol acrylate monomer was removed from the formulation and directly added to the formulation system in small molecule form according to the molar ratio of gallic acid, imidazolium-4,5-dicarboxylic acid, and 3-aminopropyltriethoxysilane. The rest is the same as in Example 2.
[0033] Comparative Example 6: Based on Example 2, the difference is that step three is changed to pre-emulsifying all monomers (soft / hard / functional monomers, silane-imidazolium-pyrogallol acrylate monomer) together into a pre-emulsion, which is added dropwise in one go as usual, without the two stages A / B, and the rest is the same as Example 2.
[0034] Comparative Example 7: Based on Example 2, the difference is that the adhesive preparation method was changed to use only persulfate as the initiation system, and sodium bisulfite, the reducing agent, was not added. The rest is the same as Example 2.
[0035] Performance testing: The water-based anti-corrosion and environmentally friendly adhesives prepared in Examples 1-3 and Comparative Examples 1-7 were subjected to performance testing. The test items and methods are as follows: 1. Polymerization conversion rate (%): determined by gravimetric method. A small amount of emulsion was weighed, dried to constant weight, and the ratio of polymer solids content to theoretical feed amount was calculated.
[0036] 2. Adhesion (MPa): According to GB / T 5210-2006 "Paints and Varnishes - Pull-off Adhesion Test", a film was prepared on a standard tinplate, and the adhesion of the dry film to the substrate was tested.
[0037] 3. Tensile shear strength: The test shall be conducted in accordance with GB / T 7124-2008 "Determination of tensile shear strength of adhesives (rigid material to rigid material)".
[0038] 4. Room Temperature Water Resistance (Tensile Shear Strength Retention Rate) Test: Following the general practice for water resistance testing of adhesives, tensile shear specimens prepared according to GB / T 7124-2008 were placed at 23±2℃ and 50%±5% relative humidity for 7 days, and the initial tensile shear strength τ0 was measured. Specimens prepared in the same batch were completely immersed in a 3.5% NaCl aqueous solution at 23±2℃ for 7 consecutive days. After immersion, the specimens were removed, surface moisture was wiped off with filter paper, and the specimens were placed in a standard environment for 2 hours before measuring the tensile shear strength τ1 after immersion. The strength retention rate was calculated using the formula R=τ1 / τ0×100%. At least 5 specimens were used in each group, and the average value was taken.
[0039] 5. Salt water resistance: Immerse the cured film in a 3.5% NaCl solution and record the time of bubbling and peeling.
[0040] 6. Salt spray resistance (h): According to GB / T 10125-2021 "Artificial Atmosphere Corrosion Test - Salt Spray Test", a neutral salt spray test (NSS) was conducted on the sample coated with adhesive, and the time when the surface rust area reached 5% was recorded.
[0041] 7. Monomer Residual Rate (%): The residual amount of unreacted monomers (especially soft acrylic acid monomers and silane-imidazol-pyrogallol acrylate monomers) in the emulsion was determined by gas chromatography (GC).
[0042] 8. Emulsion stability: (1) Mechanical stability: The emulsion was centrifuged and stirred at 4000 rpm for 30 min, and observed whether it separated into layers, broke emulsion or gelled.
[0043] (2) Storage stability: The emulsion was sealed and stored in a 50°C oven for 7 days, and the changes in its state were observed.
[0044] Table 1. Performance test results of the examples and comparative examples.
[0045] Data Analysis: Table 1 shows that the water-based anti-corrosion and environmentally friendly adhesives prepared in Examples 1-3 all exhibit extremely high polymerization conversion rates and excellent emulsion stability, demonstrating no gelation, no layering, and no emulsion breakage. They also exhibit excellent initial adhesion, tensile shear strength, and outstanding salt water and salt spray resistance. Example 2 shows the best performance across all indicators. The data from Examples 1 and 3 are highly similar to those of Example 2 and fall within a reasonable fluctuation range. This indicates that the silane-imidazolium-pyrogallol acrylate monomer dosage and preparation process determined in this invention have good reproducibility and stability.
[0046] Compared to Example 2, Comparative Examples 1-3 used Products 2, 3, and 4 to replace the silane-imidazol-pyrogallol acrylate monomer, respectively. Because all three lacked acrylate double bonds, they could not participate in copolymerization, resulting in a significant decrease in performance. Specifically, Comparative Example 1 experienced a reduced conversion rate due to the lack of grafting and the inhibition of polymerization by phenolic hydroxyl groups; in Comparative Example 2, the silane groups underwent self-condensation in a free state, leading to emulsion gelation and loss of stability; although Comparative Example 3 possessed a functional backbone, it could not bond to the polymer chain, and the free Product 4 severely inhibited polymerization, resulting in extremely low conversion and the worst mechanical properties of the adhesive layer.
[0047] Compared with Example 2, Comparative Example 4 was a blank sample. Although the conversion rate was normal, the adhesion, tensile shear strength and salt spray resistance were significantly reduced. This is because Comparative Example 4 did not add any anti-corrosion functional groups and silane coupling agents, lacked the corrosion inhibition effect of gallic acid and imidazole, and lacked siloxane chemical bonding between the polymer chain and the metal substrate, resulting in weak interfacial bonding and inability to block the penetration of corrosive media.
[0048] Compared to Example 2, Comparative Example 5 showed acceptable initial tensile shear strength, but its strength retention rate decreased significantly after immersion in water, and its salt spray resistance was significantly lower than that of Example 2. This is because Comparative Example 5 directly added small molecule compounds, which were not chemically bonded to the polymer chains. These small molecules were prone to migration and loss in a water immersion environment, leading to interfacial adhesion failure and an inability to maintain anti-corrosion function for a long time.
[0049] Compared to Example 2, Comparative Example 6 showed a lower polymerization conversion rate, slight stratification in mechanical stability, and inferior bonding strength and corrosion resistance compared to Example 2. This is because Comparative Example 6 employed a one-time drop-addition process, resulting in a large presence of phenolic hydroxyl-containing silane-imidazolium-pyrogallol acrylate monomers in the early stages of the reaction. This strong polymerization inhibition reduced polymerization efficiency, and the prolonged residence time of unreacted silanes in water increased the risk of self-condensation, affecting the quality of the final film.
[0050] Compared with Example 2, Comparative Example 7 had a higher monomer residual rate, and its mechanical and anti-corrosion performance indicators were slightly lower than those of Example 2. This is because Comparative Example 7 only used persulfate thermal initiation and lacked the synergistic effect of sodium bisulfite reducing agent. As a result, the free radical activity generated by the initiation system was insufficient to overcome the polymerization inhibition effect of phenolic hydroxyl groups, which reduced the degree of polymerization reaction. Some monomers did not participate in the reaction, affecting the crosslinking density and compactness of the film.
[0051] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.
Claims
1. A water-based anti-corrosion and environmentally friendly adhesive, characterized in that, The product comprises the following components in parts by weight: 30-50 parts of soft acrylic monomer, 20-40 parts of hard acrylic monomer, 0.5-10 parts of functional monomer, 2-8 parts of silane-imidazolium-pyrogallol acrylate monomer, 1-5 parts of emulsifier, 0.2-1.0 parts of initiator, 0.1-0.5 parts of pH buffer, 100-300 parts of deionized water, 0.5-2.0 parts of pH adjuster, 1-5 parts of film-forming aid, and 0.1-0.3 parts of defoamer; wherein the soft acrylic monomer is selected from at least one of butyl acrylate and ethylhexyl acrylate; the hard acrylic monomer is selected from at least one of methyl methacrylate and vinyl acetate; and the functional monomer... The ingredients are selected from at least one of hydroxyethyl acrylate, hydroxybutyl acrylate, hydroxypropyl acrylate, and acrylamide; the emulsifier is fatty alcohol polyoxyethylene ether or a compound of fatty alcohol polyoxyethylene ether and anionic emulsifier; the initiator is selected from at least one of ammonium persulfate, potassium persulfate, and sodium persulfate, forming a redox initiation system with sodium bisulfite, wherein the molar ratio of oxidizing initiator to reducing initiator is 1:(0.3-0.5); the pH buffer is at least one of sodium bicarbonate or sodium dihydrogen phosphate; the pH adjuster is ammonia; the film-forming aid is propylene glycol methyl ether acetate; and the defoamer is selected from at least one of organosilicon or mineral oil.
2. The water-based anti-corrosion and environmentally friendly adhesive according to claim 1, characterized in that, The method for preparing the silane-imidazol-pyrogallol acrylate monomer includes the following steps: S1: Trimethylolpropane and pentaerythritol glycidyl ether were added to a dry reactor, along with anhydrous 1,4-dioxane and the catalyst tetrabutylammonium bromide. The mixture was stirred at room temperature for 30-40 minutes, then heated to 40-60°C and reacted for 4-8 hours. After removing the solvent and low-boiling-point substances by rotary evaporation, the mixture was vacuum dried at 40-60°C for 8-12 hours to obtain product 1 containing multiple hydroxyl groups. S2: Gallic acid, N,N'-dicyclohexylcarbodiimide (DCC), and 4-dimethylaminopyridine (DMAP) were added to a dry reactor. Anhydrous dichloromethane was added, and the mixture was stirred at 0-5°C for 30-40 min. Anhydrous dichloromethane solution of product 1 was slowly added dropwise at a molar ratio of gallic acid to hydroxyl groups in product 1 of (0.3-0.5):
1. After the addition was completed, the temperature was raised to 20-25°C and the reaction was carried out for 8-10 h. After filtration, the filtrate was washed successively with 5-8% dilute hydrochloric acid, saturated sodium bicarbonate solution, and saturated brine. The organic phase was dried over anhydrous sodium sulfate and concentrated by rotary evaporation. The product 2 was purified by silica gel column chromatography. S3: Imidazole-4,5-dicarboxylic acid and anhydrous DMF were added to the reactor and stirred to dissolve. Then, 1-hydroxybenzotriazole HOBt and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride EDCI were added and stirred at room temperature for 30-40 min. Then, 3-aminopropyltriethoxysilane was added dropwise and stirred at room temperature for 10-12 h. The reaction solution was poured into ice water and stirred for extraction. The organic phases were combined, washed and dried to obtain product 3. S4: In the dry reactor, product 3, N,N ， - dicyclohexyl carbodiimide DCC, 4-dimethylamino pyridine DMAP, anhydrous dichloromethane was added, stirred at 0-5°C for 30-40 min, anhydrous dichloromethane solution of product 2 was added dropwise at a molar ratio of product 3 to the remaining hydroxyl group in product 2 of (0.4-0.6): 1, after dropping, the temperature was increased to room temperature and reacted for 8-12 h. The filtrate was obtained by filtration, washed with saturated brine for 3-4 times, the organic phase was dried over anhydrous sodium sulfate and concentrated by rotary evaporation, and product 4 was obtained by silica gel column chromatography. S5: Dissolve product 4 in anhydrous dichloromethane, add hydroquinone, then add triethylamine, cool to 0-5℃, and slowly add an anhydrous dichloromethane solution of acryloyl chloride with a molar ratio of 1.0-1.1:1 to the remaining hydroxyl groups in product 4 at a molar ratio of 1.0-1.1:
1. After the addition is complete, continue the reaction at 0-5℃ for 1-2 hours, then allow it to rise naturally to room temperature and stir for 3-4 hours. Filter to obtain the filtrate, wash it successively with dilute hydrochloric acid, saturated sodium bicarbonate solution, and saturated brine, dry the organic phase with anhydrous sodium sulfate, concentrate by rotary evaporation, purify by silica gel column chromatography, and dry under vacuum to obtain the silane-imidazolium-pyrogallol acrylate monomer.
3. The water-based anti-corrosion and environmentally friendly adhesive according to claim 2, characterized in that, In step S1, the molar ratio of pentaerythritol glycidyl ether to trimethylolpropane is 1:(3.0-4.0).
4. The water-based anti-corrosion and environmentally friendly adhesive according to claim 2, characterized in that, In step S2, the gallic acid, N,N ， The molar ratio of -dicyclohexylcarbodiimide (DCC) to 4-dimethylaminopyridine (DMAP) is 1:(1.0-1.2):(0.05-0.1).
5. The water-based anti-corrosion and environmentally friendly adhesive according to claim 2, characterized in that, In step S3, the molar ratio of imidazole-4,5-dicarboxylic acid to 3-aminopropyltriethoxysilane is 1:(0.9-1.0).
6. The water-based anti-corrosion and environmentally friendly adhesive according to claim 2, characterized in that, In step S5, the mass fraction of the dilute hydrochloric acid is 5-8%.
7. A method for preparing a water-based anti-corrosion and environmentally friendly adhesive according to claim 1, characterized in that, Includes the following steps: Step 1: Preparation of pre-emulsion Solution A: Add some deionized water and emulsifier to the reaction vessel, stir evenly, then add soft acrylic acid monomer, hard acrylic acid monomer, and functional monomer, stir at high speed for 30-40 minutes to obtain Solution A, for later use. Solution B: Take another portion of deionized water and emulsifier, add silane-imidazol-pyrogallol acrylate monomer, stir at high speed for 20-30 minutes to obtain solution B, and set aside for later use; Step 2: Seed emulsion preparation Take 10-15% of the total amount of liquid A and add it to a four-necked flask equipped with a condenser and a stirrer. Heat the mixture to 70-80℃, add 1 / 3-1 / 2 of the formula amount of the oxidized initiator component and the reduced initiator component, and react for 15-30 minutes to obtain the seed emulsion. Step 3: Segmented polymerization and pH control Phase 1: Add the remaining solution A and the remaining oxidizing initiator components dropwise into a four-necked flask simultaneously, controlling the dropping rate to be completed within 1.5-2.0 hours, at a dropping temperature of 70-80℃; during this phase, control the pH of the system to 5.5-6.5 by adding a pH buffer. Phase 2: After the addition of solution A is completed, continue to add solution B, controlling the dropping rate to be completed within 1.0-1.5 hours, and maintaining the dropping temperature at 75-80℃; After the addition is complete, continue the reaction at 80-85℃ for 1.5-2 hours, then raise the temperature to 85-90℃ and hold for 20-30 minutes to reduce the residual monomer content. Step 4: Post-processing Cool the system from step three to below 40°C, add a pH adjuster to adjust the pH of the system to 7.0-8.0, then add a film-forming aid and a defoamer, stir at low speed for 15-20 minutes until the mixture is uniform, filter and discharge to obtain the water-based anti-corrosion and environmentally friendly adhesive.