High adhesion force epoxy zinc-rich primer and gradient curing preparation process thereof
By using modified interface additives and polyaniline/N-FrGO composite fillers, combined with gradient curing process, the problems of zinc powder sedimentation and weakened interface bonding were solved, thus improving the adhesion and anti-corrosion performance of epoxy zinc-rich primer.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- LIAONING MAIQI NEW MATERIAL GRP CO LTD
- Filing Date
- 2026-05-14
- Publication Date
- 2026-06-12
AI Technical Summary
In existing epoxy zinc-rich primers, zinc powder is prone to sedimentation, accumulation, or local agglomeration, resulting in uneven distribution of the paint film composition, affecting the continuity of the conductive path and the stability of the paint film structure. Furthermore, the bonding between zinc powder and resin weakens the wetting effect, leading to decreased adhesion and insufficient long-term anti-corrosion performance.
Modified interface additives and polyaniline/N-FrGO composite fillers are used. The catechol structure of the modified interface additives forms coordination and hydrogen bonding with the steel substrate and zinc powder surface. Combined with the π-π interaction and hydrogen bonding of the polyaniline/N-FrGO composite filler, the dispersibility and conductive contact are improved. A gradient curing process is used to preferentially cure the interface layer and promote the co-curing of the interface.
It improves the adhesion and long-term corrosion resistance of epoxy zinc-rich primer, ensures the stability of the conductive contact network between zinc powder particles, extends the penetration path of corrosive media, and enhances the shielding and protective capabilities of the coating.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of coating composition technology, specifically to a high-adhesion epoxy zinc-rich primer and its gradient curing preparation process. Background Technology
[0002] Epoxy zinc-rich primer is a type of heavy-duty anti-corrosion primer material that uses epoxy resin as the film-forming agent and zinc powder as the main anti-rust pigment. It is commonly used in bridges, storage tanks, ships, pipelines, steel structures, and marine engineering. This type of primer mainly relies on the electrochemical activity of zinc powder in the coating to provide cathodic protection to the steel substrate. At the same time, it works in conjunction with the shielding effect of the paint film formed by epoxy resin to achieve anti-corrosion protection for the metal substrate.
[0003] Existing epoxy zinc-rich primers typically contain high levels of zinc powder. However, zinc powder has a high density, making it prone to settling, accumulation, or localized agglomeration during application, leveling, and curing. This results in uneven distribution of the paint film's internal composition, affecting the continuity of conductive pathways and the stability of the film structure. Patent application CN112194954A discloses a graphene-based epoxy zinc-rich coating, composed of 50-70 parts epoxy resin, 2-8 parts graphene slurry, 40-60 parts zinc powder, 5-10 parts talc, 2-5 parts anti-settling agent, 30-40 parts polyamide curing agent, and 5-10 parts film-forming aid. It improves the system's dispersibility and corrosion resistance by partially replacing zinc powder with graphene and incorporating polyacrylate dispersants. However, high zinc powder content can also weaken the wetting and coating effect of the resin on the steel substrate surface to a certain extent, thereby reducing the adhesion of the paint film. During service, when external moisture, oxygen or salt spray gradually penetrates along the interface defects, it may further induce coating failure problems such as blistering, cracking and peeling.
[0004] Patent application CN108034294A discloses a zinc powder slurry and its coating process for improving the secondary adhesion of waterborne epoxy zinc-rich coatings. The zinc powder slurry uses a silane coupling agent, which is pre-dispersed and wetted with the zinc powder, resulting in excellent wet adhesion and significantly improving the secondary adhesion of the coating film. However, this technical solution mainly relies on the silane coupling agent to pre-coat the zinc powder surface to improve the zinc powder / resin interface bonding. While this is beneficial for improving wet and secondary adhesion, for epoxy zinc-rich primers, effective conductive contact between zinc powder particles and between zinc powder and the steel substrate is crucial for ensuring the continued effectiveness of the sacrificial anode. Pre-coating the zinc powder with the silane coupling agent may lead to a thickening of the organic layer on the zinc powder surface and an increase in interparticle contact resistance, thereby weakening the ability of some zinc powder to participate in the cathodic protection process. This poses a risk that while improving adhesion, it may also affect the conductive contact network and long-term anti-corrosion performance of the zinc-rich primer.
[0005] Therefore, there is a need to provide a high-adhesion epoxy zinc-rich primer and its gradient curing preparation process to solve the above-mentioned technical problems. Summary of the Invention
[0006] In view of this, the present invention provides a high-adhesion epoxy zinc-rich primer and its gradient curing preparation process, which can improve the overall adhesion while taking into account long-term anti-corrosion performance.
[0007] To achieve the above objectives, the present invention provides a high-adhesion epoxy zinc-rich primer, comprising component A and component B; Component A comprises the following raw materials: bisphenol A type liquid epoxy resin, modified interface additives, dispersants, defoamers, mixed solvents, fumed silica, and zinc powder, and also includes a polyaniline / N-FrGO pre-dispersion composed of polyaniline / N-FrGO composite filler and mixed solvents; Component B is a curing agent; The polyaniline / N-FrGO composite filler was obtained by adding polyaniline dispersion to N-FrGO dispersion, heating and stirring, ultrasonication, centrifugation, washing, and drying. The modified interface additive is obtained by mixing ethylene glycol diglycidyl ether, protocatechuic acid and p-toluenesulfonic acid monohydrate, heating and stirring under inert gas protection, reacting at elevated temperature, and then cooling.
[0008] This invention introduces a protocatechuic acid fragment containing a catechol structure into an epoxy chain segment, forming a modified interface aid containing a catechol structure, hydroxyl sites, and some unreacted epoxy active groups. The catechol groups in this modified interface aid have a strong affinity for metal and metal oxide surfaces. Its ortho-dihydroxyl groups can form coordination, hydrogen bonding, and polar adsorption interactions with the steel substrate surface and zinc powder surface, thereby facilitating the formation of a stable interface anchoring layer at the steel substrate / coating interface and the zinc powder / resin interface. This improves the wetting and spreading ability of the primer on the substrate surface, reduces interface contact defects, and increases the initial adhesion strength of the coating to the steel substrate. Furthermore, the retained epoxy active groups and the reacted hydroxyl sites can further participate in the cross-linking reaction of the epoxy resin / polyamide curing system, allowing it to continue co-curing with the surrounding resin network after adsorption onto the steel substrate surface or zinc powder surface. This forms a relatively stable "metal surface-catechuicol interface layer-crosslinked epoxy network" transition structure at the interface, further improving the overall adhesion of the epoxy zinc-rich primer.
[0009] In this invention, polyaniline can be bonded to the surface of nitrogen-fluorine co-doped graphene (N-FrGO) through π-π interactions and hydrogen bonding, which is beneficial for improving the dispersion state of graphene sheet fillers in the resin system and reducing their tendency to agglomerate and recombine. The uniformly dispersed polyaniline / N-FrGO composite filler can be distributed between zinc powder particles and plays a certain role in auxiliary bridging, thereby helping to improve the contact and connectivity between zinc powder particles. At the same time, the nitrogen-containing structure in N-FrGO is beneficial for regulating the electronic structure of graphene sheets, and the moderate fluorine-containing structure is beneficial for improving the surface state of the sheets and reducing the tendency of sheet recombination. This allows the composite filler to maintain a good dispersion and connectivity state in the resin / zinc powder system, thereby helping to improve the conductive transport pathway in the zinc-rich system, maintain the continuous performance of the sacrificial anode cathodic protection of zinc powder, and improve the long-term corrosion resistance of the coating. In addition, the two-dimensional lamellar structure of the composite filler can also fill and block the pores of the coating, forming a labyrinth effect, prolonging the penetration path of corrosive media in the coating, reducing the diffusion rate of moisture, oxygen and chloride ions to the surface of the metal substrate, thereby improving the shielding and protection capabilities of the coating.
[0010] Optionally, the N-FrGO dispersion is prepared by placing reduced graphene oxide and ammonium fluoride in two separate corundum boats, then inverting the corundum boat containing reduced graphene oxide above the corundum boat containing ammonium fluoride, and then placing them together in the corundum tube of a tubular furnace; after purging the furnace chamber with nitrogen for 20-30 min, the temperature is increased to 800-850℃ at a nitrogen flow rate of 50 mL / min and maintained at that temperature for 30-50 min, and then cooled to room temperature to obtain N-FrGO, which is then added to deionized water and stirred for 30-40 min, and then ultrasonically dispersed for 20-30 min; the polyaniline dispersion is prepared by adding conductive polyaniline powder to deionized water, stirring for 20-30 min, and then ultrasonically dispersing for 20-30 min.
[0011] Preferably, the tail gas generated during the reaction process to prepare N-FrGO is treated by alkaline solution absorption before being discharged.
[0012] This invention involves high-temperature treatment of reduced graphene oxide and ammonium fluoride under nitrogen protection. The active components generated from the decomposition of ammonium fluoride interact with the defect sites and active sites on the surface of reduced graphene oxide, thereby introducing fluorine and nitrogen elements into the graphene sheets to obtain fluorine-nitrogen co-doped graphene (N-FrGO). The introduction of nitrogen-containing structures helps to regulate the electronic structure of graphene and enhance electron transport capabilities; moderate fluorine-containing structures help to regulate the surface charge distribution of the sheets, weaken interlayer interactions, reduce the degree of re-stacking, and improve interlayer conductive contacts while maintaining the continuity of the graphene conductive framework.
[0013] Optionally, the N-FrGO dispersion comprises the following raw materials in parts by weight: 1-1.2 parts of reduced graphene oxide, 10-12 parts of ammonium fluoride, and 500-600 parts of deionized water; the polyaniline dispersion comprises the following raw materials in parts by weight: 0.06-0.08 parts of conductive polyaniline powder and 180-200 parts of deionized water.
[0014] Optionally, the modified interface aid is prepared by mixing 18-22 parts by weight of ethylene glycol diglycidyl ether, 2-2.2 parts by weight of protocatechuic acid and 0.2-0.25 parts by weight of p-toluenesulfonic acid monohydrate, stirring at 70-80°C for 30-40 min under nitrogen protection, increasing the temperature to 100-120°C at 2°C / min, continuing the reaction for 4-6 h, and then cooling to room temperature.
[0015] Optionally, the polyaniline / N-FrGO composite filler is obtained by adding polyaniline dispersion to N-FrGO dispersion, stirring at 75~80℃ for 1~2h, then ultrasonicating for 20~30min, centrifuging, washing with deionized water 3~5 times, and vacuum drying at 50~60℃ for 20~24h.
[0016] Optionally, the polyaniline / N-FrGO predispersant is obtained by adding 0.4 to 0.6 parts of polyaniline / N-FrGO composite filler to 3 to 5 parts of mixed solvent, magnetically stirring for 10 to 15 minutes, and then ultrasonically dispersing for 20 to 30 minutes.
[0017] Optionally, component A comprises the following raw materials in parts by weight: 90-110 parts of bisphenol A type liquid epoxy resin, 7-9 parts of modified interface additives, 0.8-1.2 parts of dispersant, 0.3-0.5 parts of defoamer, 12-15 parts of mixed solvent, 2-5 parts of fumed silica, and 700-750 parts of zinc powder, and further comprises a polyaniline / N-FrGO pre-dispersion composed of 0.4-0.6 parts of polyaniline / N-FrGO composite filler and 3-5 parts of mixed solvent; component B is 60-75 parts of curing agent; the mixed solvent is a xylene / n-butanol mixed solvent, wherein the mass ratio of xylene to n-butanol in the mixed solvent is 8:2; and the curing agent is a polyamide curing agent.
[0018] The above-mentioned component ratio is beneficial to balance the film density of the coating, the conductive contact stability of zinc powder, and the dispersibility during application. It can improve the adhesion of the primer to the substrate and enhance the shielding and protective capabilities and long-term corrosion resistance of the coating.
[0019] Preferably, the dispersant is BYK-9076 and the defoamer is BYK-054.
[0020] Optionally, a high-adhesion epoxy zinc-rich primer is prepared by uniformly mixing component A and component B and then curing for 10-20 minutes.
[0021] Optionally, component A is prepared by mixing and stirring bisphenol A type liquid epoxy resin and modified interface additives for 10-15 min, adding dispersant, defoamer and mixed solvent and stirring for 15-20 min, then slowly adding polyaniline / N-FrGO pre-dispersion and dispersing at high speed at 1200-1500 rpm for 20-30 min, followed by adding fumed silica and dispersing at high speed at 1200-1500 rpm for 20-30 min; then slowly adding zinc powder in 3-5 portions and dispersing at 1000-1200 rpm for 30-40 min, followed by vacuum degassing.
[0022] By adopting the above-mentioned stepwise addition and dispersion method, the resin and additive system is first fully mixed, and then the polyaniline / N-FrGO pre-dispersion liquid is introduced, which helps to improve the dispersion uniformity of the composite filler in the resin phase and avoid local agglomeration. Subsequently, fumed silica is added, which helps to form a stable thixotropic anti-settling system. Finally, zinc powder is added in stages and dispersed, which can reduce the risk of agglomeration caused by one-time addition and make the zinc powder more evenly distributed in the system. This helps to balance the stability of coating application, storage stability and conductive and anti-corrosion performance after film formation.
[0023] This invention also provides a gradient curing preparation process. The high-adhesion epoxy zinc-rich primer is used to prepare the paint film through the following gradient curing process, with the following steps: The epoxy zinc-rich primer is sprayed onto the surface of Q235 steel plate after sandblasting and rust removal treatment, and the dry film thickness is controlled to be 60~80μm. The plate is allowed to stand and level at 25~30℃ for 30~40min. Then, the back of the sprayed steel plate is heated at 55~60℃ for 1~2h. Finally, the plate is placed in an oven at 70~80℃ for 4~5h to bake as a whole, and the high-adhesion epoxy zinc-rich paint film is obtained.
[0024] This invention employs a gradient curing process with preferential heating on the substrate side. This process allows the interfacial layer closest to the steel substrate surface to preferentially enter the curing stage, thereby facilitating the adsorption and interfacial bonding of the modified interfacial additives on the steel substrate surface and promoting their interfacial co-curing with the epoxy resin network. This results in the preferential formation of a denser interfacial layer on the substrate surface, improving the interfacial bonding stability and adhesion strength between the paint film and the steel substrate. This invention first performs leveling at room temperature, then gently raises the temperature from the substrate side, and combines this with a subsequent overall post-curing process. This allows the interfacial layer to be established firmly first, and the upper part of the paint film to gradually complete cross-linking and densification. This helps reduce interfacial micropores and further enhances the physical shielding effect, thus improving long-term corrosion resistance.
[0025] The above-described technical solution of the present invention has at least the following beneficial effects: 1. This invention introduces protocatechuic acid fragments containing a catechol structure into epoxy segments, forming a modified interface additive containing a catechol structure, hydroxyl sites, and some unreacted epoxy active groups. Utilizing the coordination adsorption, hydrogen bonding, and polar effects of the catechol groups on the steel substrate and zinc powder surface, and combining with the participation of some unreacted epoxy active groups in co-curing, it is beneficial to form a stable transition layer at the interface. Furthermore, combined with a gradient curing process that preferentially heats the substrate side, the interfacial bonding stability can be further improved, thereby significantly enhancing the adhesion of the primer.
[0026] 2. The present invention uses polyaniline / N-FrGO composite filler, which is beneficial to improving the dispersibility of graphene fillers in the resin system, promoting the formation of conductive contact network between zinc powder particles and prolonging the cathodic protection effect, and can also utilize its two-dimensional sheet structure to generate a labyrinth barrier effect, reduce the penetration rate of corrosive media, thereby improving the long-term corrosion resistance and shielding protection capability of the coating. Detailed Implementation
[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. The described embodiments are some embodiments of the present invention, and all other embodiments obtained by those skilled in the art based on the described embodiments of the present invention are within the scope of protection of the present invention.
[0028] Example 1 22g of ethylene glycol diglycidyl ether, 2.2g of protocatechuic acid (CAS No.: 99-50-3) and 0.25g of p-toluenesulfonic acid monohydrate (CAS No.: 6192-52-5) were mixed and stirred at 80℃ for 40min under nitrogen protection. The temperature was then increased to 120℃ at a rate of 2℃ / min, and the reaction was continued for 6h. After cooling to room temperature, the modified interface additive was obtained.
[0029] 1.2 g of reduced graphene oxide (rGO) and 12 g of ammonium fluoride were placed in two separate corundum boats. The corundum boat containing rGO was then inverted on top of the corundum boat containing ammonium fluoride, and both were placed in the corundum tube of a tube furnace. After purging the furnace cavity with nitrogen for 30 min, the temperature was increased to 850 °C at a rate of 5 °C / min under a nitrogen flow rate of 50 mL / min, and the reaction was held at this temperature for 50 min. The exhaust gas generated during the reaction was treated by alkaline solution before being discharged. After cooling to room temperature, fluorine-nitrogen co-doped graphene (N-FrGO) was obtained. It was added to 600 mL of deionized water and stirred for 40 min, then ultrasonically dispersed for 30 min to obtain an N-FrGO dispersion. 0.08 g of conductive polyaniline powder (CAS No.: 25233-30-1) was added to 200 mL of deionized water, stirred for 30 min, and ultrasonically dispersed for 30 min to obtain a polyaniline dispersion. This dispersion was then added to an N-FrGO dispersion, stirred at 80 °C for 2 h, ultrasonically treated for 30 min, centrifuged, washed 5 times with deionized water, and finally vacuum dried at 60 °C for 24 h to obtain a polyaniline / N-FrGO composite filler. 0.6 g of the polyaniline / N-FrGO composite filler was added to 5 g of xylene / n-butanol mixed solvent, magnetically stirred for 15 min, and then ultrasonically dispersed for 30 min to obtain a polyaniline / N-FrGO pre-dispersion.
[0030] 110g of bisphenol A type liquid epoxy resin (model E-51) and 9g of modified interface additive were mixed and stirred for 15min. Then, 1.2g of dispersant BYK-9076, 0.5g of defoamer BYK-054, and 15g of xylene / n-butanol mixed solvent (xylene to n-butanol mass ratio 8:2) were added. Stirring continued for 20min. Next, polyaniline / N-FrGO pre-dispersion was slowly added and dispersed at 1500rpm for 30min. Then, 5g of fumed silica was added and dispersed at 1500rpm for another 30min. Finally, 750g of zinc powder was slowly added in five portions and dispersed at 1200rpm for 40min. Vacuum degassing was performed to obtain component A. 75g of polyamide curing agent (CAS No.: 68410-23-1) was used as component B. For use, components A and B were mixed evenly and cured for 20min to obtain a high-adhesion epoxy zinc-rich primer.
[0031] The high-adhesion epoxy zinc-rich primer was prepared into a coating film through the following gradient curing process, as detailed below: The high-adhesion epoxy zinc-rich primer was sprayed onto the surface of Q235 steel plate after sandblasting and rust removal. The dry film thickness was controlled to be 80 μm. The plate was allowed to stand and level at 30℃ for 40 min. Then, the sprayed steel plate was placed on a 60℃ hot plate and heated with the back of the steel plate in contact with the hot plate for 2 h. Finally, it was transferred to an 80℃ oven for baking for 5 h to obtain a high-adhesion epoxy zinc-rich paint film.
[0032] Example 2 18g of ethylene glycol diglycidyl ether, 2g of protocatechuic acid (CAS No.: 99-50-3) and 0.2g of p-toluenesulfonic acid monohydrate (CAS No.: 6192-52-5) were mixed and stirred at 70℃ for 30min under nitrogen protection. The temperature was then increased to 100℃ at a rate of 2℃ / min, and the reaction was continued for 4h. After cooling to room temperature, the modified interface additive was obtained.
[0033] 1g of reduced graphene oxide (rGO) and 10g of ammonium fluoride were placed in two separate corundum boats. The corundum boat containing rGO was then inverted on top of the corundum boat containing ammonium fluoride, and then both were placed in the corundum tube of a tubular furnace. After purging the furnace cavity with nitrogen for 20 min, the temperature was increased to 800℃ at a rate of 5℃ / min under a nitrogen flow rate of 50 mL / min, and the reaction was held at this temperature for 30 min. The tail gas generated during the reaction was treated by alkaline solution before being discharged. After cooling to room temperature, nitrogen-fluorine co-doped graphene (N-FrGO) was obtained. It was added to 500 mL of deionized water and mixed and stirred for 30 min, and then ultrasonically dispersed for 20 min to obtain an N-FrGO dispersion. 0.6 g of conductive polyaniline powder (CAS No.: 25233-30-1) was added to 180 mL of deionized water, stirred for 20 min, and ultrasonically dispersed for 20 min to obtain a polyaniline dispersion. This dispersion was then added to an N-FrGO dispersion, stirred at 75 °C for 1 h, ultrasonically treated for 20 min, centrifuged, washed three times with deionized water, and finally vacuum dried at 50 °C for 20 h to obtain a polyaniline / N-FrGO composite filler. 0.4 g of the polyaniline / N-FrGO composite filler was added to 3 g of xylene / n-butanol mixed solvent, magnetically stirred for 10 min, and then ultrasonically dispersed for 20 min to obtain a polyaniline / N-FrGO pre-dispersion.
[0034] 90g of bisphenol A type liquid epoxy resin (model E-51) and 7g of modified interface additive were mixed and stirred for 10min. Then, 0.8g of dispersant BYK-9076, 0.3g of defoamer BYK-054, and 12g of xylene / n-butanol mixed solvent (xylene to n-butanol mass ratio 8:2) were added. Stirring continued for 15min. Next, polyaniline / N-FrGO pre-dispersion was slowly added and dispersed at 1200rpm for 20min. Then, 2g of fumed silica was added and dispersed at 1200rpm for another 20min. Finally, 700g of zinc powder was slowly added in three portions and dispersed at 1000rpm for 30min. Vacuum degassing was performed to obtain component A. 60g of polyamide curing agent (CAS No.: 68410-23-1) was used as component B. For use, component A and component B were mixed evenly and allowed to cure for 10min to obtain a high-adhesion epoxy zinc-rich primer.
[0035] The high-adhesion epoxy zinc-rich primer was prepared into a coating film through the following gradient curing process, as detailed below: The high-adhesion epoxy zinc-rich primer was sprayed onto the surface of Q235 steel plate after sandblasting and rust removal. The dry film thickness was controlled to be 60μm. The plate was allowed to stand and level at 25℃ for 30min. Then, the sprayed steel plate was placed on a 55℃ hot plate and heated with the back of the steel plate in contact with the hot plate for 1h. Finally, it was transferred to a 70℃ oven for baking for 4h to obtain a high-adhesion epoxy zinc-rich paint film.
[0036] Example 3 18.8 g of ethylene glycol diglycidyl ether, 2.05 g of protocatechuic acid (CAS No.: 99-50-3) and 0.21 g of p-toluenesulfonic acid monohydrate (CAS No.: 6192-52-5) were mixed and stirred at 72 °C for 32 min under nitrogen protection. The temperature was then increased to 105 °C at a rate of 2 °C / min, and the reaction was continued for 4.5 h. After cooling to room temperature, the modified interface additive was obtained.
[0037] 1.05 g of reduced graphene oxide (rGO) and 10.5 g of ammonium fluoride were placed separately in two corundum boats. The corundum boat containing rGO was then inverted on top of the corundum boat containing ammonium fluoride, and then both were placed in the corundum tube of a tube furnace. After purging the furnace cavity with nitrogen for 22 min, the temperature was increased to 810 °C at a rate of 5 °C / min under a nitrogen flow rate of 50 mL / min, and the reaction was held at this temperature for 35 min. The exhaust gas generated during the reaction was treated by alkaline solution before being discharged. After cooling to room temperature, nitrogen-fluorine co-doped graphene (N-FrGO) was obtained. It was added to 525 mL of deionized water and mixed and stirred for 32 min, then ultrasonically dispersed for 22 min to obtain an N-FrGO dispersion. 0.0 62g of conductive polyaniline powder (CAS No.: 25233-30-1) was added to 185mL of deionized water, stirred for 22min, and ultrasonically dispersed for 22min to obtain a polyaniline dispersion. This dispersion was then added to an N-FrGO dispersion, stirred at 76℃ for 1.2h, ultrasonically treated for 22min, centrifuged, washed four times with deionized water, and finally vacuum dried at 52℃ for 21h to obtain a polyaniline / N-FrGO composite filler. 0.45g of the polyaniline / N-FrGO composite filler was added to 3.5g of a xylene / n-butanol mixed solvent, magnetically stirred for 11min, and then ultrasonically dispersed for 22min to obtain a polyaniline / N-FrGO pre-dispersion.
[0038] 94g of bisphenol A type liquid epoxy resin (model E-51) was mixed with 7.5g of modified interface additive and stirred for 11min. 0.9g of dispersant BYK-9076, 0.35g of defoamer BYK-054, and 12.5g of xylene / n-butanol mixed solvent were added. The mass ratio of xylene to n-butanol in the mixed solvent was 8:2. The mixture was stirred for another 16min. Then, polyaniline / N-FrGO pre-dispersion was slowly added and dispersed at 1250rpm for 22min. Subsequently, 3g of fumed silica was added and dispersed at 1250rpm for another 22min. Then, 710g of zinc powder was slowly added in four portions and dispersed at 1050rpm for another 32min. Vacuum degassing was performed to obtain component A. 63g of polyamide curing agent (CAS No.: 68410-23-1) was used as component B. When using, mix component A and component B evenly and allow to mature for 12 minutes to obtain a high-adhesion epoxy zinc-rich primer.
[0039] The high-adhesion epoxy zinc-rich primer was prepared into a coating film through the following gradient curing process, as detailed below: The high-adhesion epoxy zinc-rich primer was sprayed onto the surface of Q235 steel plate after sandblasting and rust removal. The dry film thickness was controlled at 64μm. The plate was allowed to stand and level at 26℃ for 32min. Then, the sprayed steel plate was placed on a 56℃ hot plate and heated with the back of the steel plate in contact with the hot plate for 1.2h. Finally, it was placed in a 72℃ oven for overall baking for 4.2h to obtain a high-adhesion epoxy zinc-rich paint film.
[0040] Example 4 21g of ethylene glycol diglycidyl ether, 2.15g of protocatechuic acid (CAS No.: 99-50-3) and 0.24g of p-toluenesulfonic acid monohydrate (CAS No.: 6192-52-5) were mixed and stirred at 78℃ for 38min under nitrogen protection. The temperature was then increased to 115℃ at a rate of 2℃ / min, and the reaction was continued for 5.5h. After cooling to room temperature, the modified interface additive was obtained.
[0041] 1.15 g of reduced graphene oxide (rGO) and 11.5 g of ammonium fluoride were placed in two separate corundum boats. The corundum boat containing rGO was then inverted on top of the corundum boat containing ammonium fluoride, and then both were placed in the corundum tube of a tube furnace. After purging the furnace chamber with nitrogen for 28 min, the temperature was increased to 840 °C at a rate of 5 °C / min under a nitrogen flow rate of 50 mL / min, and the reaction was held at this temperature for 45 min. The tail gas generated during the reaction was treated by alkaline solution before being discharged. After cooling to room temperature, nitrogen-fluorine co-doped graphene (N-FrGO) was obtained. It was added to 575 mL of deionized water and mixed and stirred for 38 min, and then ultrasonically dispersed for 28 min to obtain an N-FrGO dispersion. 0.7 g of conductive polyaniline powder (CAS No.: 25233-30-1) was added to 195 mL of deionized water, stirred for 28 min, and ultrasonically dispersed for 28 min to obtain a polyaniline dispersion. This dispersion was then added to an N-FrGO dispersion, stirred at 79 °C for 1.8 h, ultrasonically treated for 28 min, centrifuged, washed 5 times with deionized water, and finally vacuum dried at 58 °C for 23 h to obtain a polyaniline / N-FrGO composite filler. 0.55 g of the polyaniline / N-FrGO composite filler was added to 4.5 g of xylene / n-butanol mixed solvent, magnetically stirred for 13 min, and then ultrasonically dispersed for 28 min to obtain a polyaniline / N-FrGO pre-dispersion.
[0042] 106g of bisphenol A type liquid epoxy resin (model E-51) was mixed with 8.5g of modified interface additive and stirred for 13min. 1.1g of dispersant BYK-9076, 0.45g of defoamer BYK-054, and 14.2g of xylene / n-butanol mixed solvent were added. The mass ratio of xylene to n-butanol in the mixed solvent was 8:2. The mixture was stirred for another 19min. Then, polyaniline / N-FrGO pre-dispersion was slowly added and dispersed at 1420rpm for 28min. Subsequently, 4.5g of fumed silica was added and dispersed at 1420rpm for another 28min. Then, 738g of zinc powder was slowly added in 5 portions and dispersed at 1150rpm for another 38min. Vacuum degassing was performed to obtain component A. 72g of polyamide curing agent (CAS No.: 68410-23-1) was used as component B. When using, mix component A and component B evenly and allow to mature for 18 minutes to obtain a high-adhesion epoxy zinc-rich primer.
[0043] The high-adhesion epoxy zinc-rich primer was prepared into a coating film through the following gradient curing process, as detailed below: The high-adhesion epoxy zinc-rich primer was sprayed onto the surface of Q235 steel plate after sandblasting and rust removal. The dry film thickness was controlled at 75μm. The plate was allowed to stand and level at 29℃ for 38min. Then, the sprayed steel plate was placed on a 59℃ hot plate and heated with the back of the steel plate in contact with the hot plate for 1.8h. Finally, it was placed in a 78℃ oven for overall baking for 4.8h to obtain a high-adhesion epoxy zinc-rich paint film.
[0044] Example 5 20g of ethylene glycol diglycidyl ether, 2.1g of protocatechuic acid (CAS No.: 99-50-3) and 0.23g of p-toluenesulfonic acid monohydrate (CAS No.: 6192-52-5) were mixed and stirred at 75℃ for 35min under nitrogen protection. The temperature was then increased to 110℃ at a rate of 2℃ / min, and the reaction was continued for 5h. After cooling to room temperature, the modified interface additive was obtained.
[0045] 1.1 g of reduced graphene oxide (rGO) and 11 g of ammonium fluoride were placed separately in two corundum boats. The corundum boat containing rGO was then inverted on top of the corundum boat containing ammonium fluoride, and then both were placed in the corundum tube of a tube furnace. After purging the furnace cavity with nitrogen for 25 min, the temperature was increased to 825 °C at a rate of 5 °C / min under a nitrogen flow rate of 50 mL / min, and the reaction was held at this temperature for 40 min. The exhaust gas generated during the reaction was treated by alkaline solution before being discharged. After cooling to room temperature, nitrogen-fluorine co-doped graphene (N-FrGO) was obtained. It was added to 550 mL of deionized water and mixed and stirred for 35 min, then ultrasonically dispersed for 25 min to obtain an N-FrGO dispersion. 0.0 65g of conductive polyaniline powder (CAS No.: 25233-30-1) was added to 190mL of deionized water, stirred for 25min, and ultrasonically dispersed for 25min to obtain a polyaniline dispersion. This dispersion was then added to an N-FrGO dispersion, stirred at 78℃ for 1.5h, ultrasonically treated for 25min, centrifuged, washed four times with deionized water, and finally vacuum dried at 55℃ for 22h to obtain a polyaniline / N-FrGO composite filler. 0.5g of the polyaniline / N-FrGO composite filler was added to 4g of xylene / n-butanol mixed solvent, magnetically stirred for 12min, and then ultrasonically dispersed for 25min to obtain a polyaniline / N-FrGO pre-dispersion.
[0046] 100g of bisphenol A type liquid epoxy resin (model E-51) was mixed with 8g of modified interface additive and stirred for 12min. 1.0g of dispersant BYK-9076, 0.4g of defoamer BYK-054, and 13.5g of xylene / n-butanol mixed solvent were added. The mass ratio of xylene to n-butanol in the mixed solvent was 8:2. The mixture was stirred for another 18min. Then, polyaniline / N-FrGO pre-dispersion was slowly added and dispersed at 1350rpm for 25min. Subsequently, 4g of fumed silica was added and dispersed at 1350rpm for another 25min. Then, 725g of zinc powder was slowly added in four portions and dispersed at 1100rpm for another 35min. Vacuum degassing was performed to obtain component A. 68g of polyamide curing agent (CAS No.: 68410-23-1) was used as component B. When using, mix component A and component B evenly and allow to mature for 15 minutes to obtain a high-adhesion epoxy zinc-rich primer.
[0047] The high-adhesion epoxy zinc-rich primer was prepared into a coating film through the following gradient curing process, as detailed below: The high-adhesion epoxy zinc-rich primer was sprayed onto the surface of Q235 steel plate after sandblasting and rust removal. The dry film thickness was controlled at 70 μm. The plate was allowed to stand and level at 28℃ for 35 min. Then, the sprayed steel plate was placed on a 58℃ hot plate and heated with the back of the steel plate in contact with the hot plate for 1.5 h. Finally, it was placed in a 75℃ oven for overall baking for 4.5 h to obtain a high-adhesion epoxy zinc-rich paint film.
[0048] The present invention also includes comparative examples and related experiments.
[0049] Comparative Example 1 Compared with Example 5, the only difference is that polyaniline / N-FrGO composite filler was not added, but an equal amount of xylene / n-butanol mixed solvent was added to make up the amount of solvent in the pre-dispersion liquid. The other raw materials and dosages are completely the same, and a high-adhesion epoxy zinc-rich primer is finally obtained. The same curing preparation process is then used to prepare a high-adhesion epoxy zinc-rich paint film.
[0050] Comparative Example 2 Compared with Example 5, the only difference is that 0.5g of N-FrGO was added to 4g of xylene / n-butanol mixed solvent, magnetically stirred for 12min, and then ultrasonically dispersed for 25min to obtain N-FrGO pre-dispersion. This N-FrGO pre-dispersion was used to replace the polyaniline / N-FrGO pre-dispersion in Example 5. The other raw materials, dosages, and preparation steps were completely the same to obtain a high-adhesion epoxy zinc-rich primer. The same curing process was then used to prepare a high-adhesion epoxy zinc-rich coating film.
[0051] Comparative Example 3 Compared with Example 5, the only difference is that no modified interface additive was added to the high-adhesion epoxy zinc-rich primer, while the other raw materials, dosages and preparation steps were completely the same, and a high-adhesion epoxy zinc-rich primer was obtained; and a high-adhesion epoxy zinc-rich film was further obtained using the same curing preparation process.
[0052] Comparative Example 4 The high-adhesion epoxy zinc-rich primer prepared in Example 5 was sprayed onto the surface of Q235 steel plate after sandblasting and rust removal treatment. The dry film thickness was controlled to be 70 μm. After standing and leveling at 28°C for 35 min, it was directly transferred to a 75°C oven for overall baking for 4.5 h to finally obtain a high-adhesion epoxy zinc-rich paint film.
[0053] Comparative Example 5 The high-adhesion epoxy zinc-rich primer prepared in Example 5 was sprayed onto the surface of Q235 steel plate after sandblasting and rust removal treatment. The dry film thickness was controlled to be 70 μm. After standing and leveling at 28°C for 35 min, it was naturally cured at 25°C for 7 days to finally obtain a high-adhesion epoxy zinc-rich paint film.
[0054] Performance testing I. The density, viscosity, and storage stability of component A in the high-adhesion epoxy zinc-rich primers prepared in Examples 1-5 and Comparative Examples 1-3 were tested. The density test was conducted according to GB / T6750-2007 "Determination of density of paints and varnishes - Specific gravity bottle method", the viscosity test was conducted according to GB / T9751.1-2008 "Determination of viscosity of paints and varnishes using rotational viscometer - Part 1: Cone-plate viscometer operating at high shear rates", and the storage stability test was conducted according to GB / T6753.3-1986 "Test method for storage stability of coatings". The specific performance test results are shown in Table 1.
[0055] Table 1 As shown in Table 1, the high-adhesion epoxy zinc-rich primer component A prepared in Examples 1-5 all exhibit good application applicability and storage stability, with densities ranging from 3.52 to 3.60 g / cm³. 3 Within the specified range, the viscosity was concentrated in the range of 2350~2510 mPa·s. After storage at 50℃ for 30 days, no obvious agglomeration or stratification was observed, indicating that within the formulation range defined by this invention, each embodiment can balance high solid content, suitable application viscosity, and good storage stability. Comparative Example 1, lacking the polyaniline / N-FrGO composite filler, showed slight sedimentation; Comparative Example 2, using N-FrGO to replace the polyaniline / N-FrGO composite filler, also showed localized agglomeration accompanied by slight stratification; Comparative Example 3, lacking the modified interface additive, exhibited the most obvious sedimentation and stratification phenomena.
[0056] II. The high-adhesion epoxy zinc-rich coatings prepared in Examples 1-5 and Comparative Examples 1-5 were subjected to relevant performance tests, as detailed below: 1. Adhesion test: Conducted according to GB / T9286-2021 "Paints and Varnishes - Cross-cut Test"; 2. Impact resistance test: Conducted according to GB / T1732-2020 "Determination of Impact Resistance of Coatings"; 3. Conductivity and Protection Performance Tests: The paint film samples prepared in Examples 1-5 and Comparative Examples 1-5 were immersed in a 3.5% NaCl solution, and the cathodic protection period was tested by electrochemical experiments. The criterion for determining cathodic protection failure was when the open-circuit potential of the paint film sample relative to the saturated calomel electrode shifted positively to above -0.85V, and the time corresponding to reaching this criterion was recorded as the cathodic protection period. Furthermore, the impedance value of the coating sample in the low-frequency region (0.01Hz) was tested when cathodic protection failure occurred. 4. Corrosion resistance test: The paint film samples prepared in Examples 1-5 and Comparative Examples 1-5 were scratched on the coating surface using a scribing tool with a width of 0.5 mm. Then, a neutral salt spray test was conducted according to GB / T10125-2021 "Civilization Test in Artificial Atmosphere" for 1000 h. After the test, the corrosion spread in the scratched area of the coating was observed and the average corrosion width was measured. The specific test results are shown in Table 2.
[0057] Table 2 As shown in Table 2, the high-adhesion epoxy zinc-rich coatings prepared in Examples 1-5 all exhibit excellent adhesion, impact resistance, conductivity, protective properties, and corrosion resistance. The cross-cut adhesion of each example reaches grade 0, the impact resistance is within the range of 45-50 kg·cm, the cathodic protection period is within the range of 156-168 days, and the low-frequency impedance at cathodic protection failure reaches 1.15 × 10⁻⁶. 6 ~1.38×10 6 Ω·cm 2 Furthermore, the average corrosion width of the salt spray over 1000 hours was controlled within the range of 1.2 to 1.7 mm, indicating that the coating film with high adhesion and long-lasting anti-corrosion capability can be obtained within the range of the formula and gradient curing process defined by the present invention.
[0058] In Comparative Example 1, the absence of polyaniline / N-FrGO composite filler shortened the cathodic protection period to 82 days, and the average salt spray corrosion width increased to 6.9 mm after 1000 hours. In Comparative Example 2, replacing the polyaniline / N-FrGO composite filler with N-FrGO, both the cathodic protection period and salt spray corrosion width were better than Comparative Example 1, but still significantly lower than Example 5. In Comparative Example 3, the absence of modified interface additives reduced the cross-cut adhesion to level 3 and the impact resistance to 25 kg·cm, significantly affecting the impact resistance. Furthermore, Comparative Examples 4 and 5 further demonstrated the importance of the gradient curing process. After using only an overall oven for curing, Comparative Example 4 showed lower adhesion, impact resistance, cathodic protection period, and corrosion resistance than Example 5. After using room temperature natural curing, all properties of Comparative Example 5 further decreased, indicating that the gradient curing method used in this invention is beneficial for improving film adhesion and further extending the cathodic protection period.
[0059] The above are preferred embodiments of the present invention. Those skilled in the art can make several improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A high-adhesion epoxy zinc-rich primer, characterized in that, Includes component A and component B; Component A comprises the following raw materials: bisphenol A type liquid epoxy resin, modified interface additives, dispersants, defoamers, mixed solvents, fumed silica, and zinc powder, and also includes a polyaniline / N-FrGO pre-dispersion composed of polyaniline / N-FrGO composite filler and mixed solvents; Component B is a curing agent; The polyaniline / N-FrGO composite filler was obtained by adding polyaniline dispersion to N-FrGO dispersion, heating and stirring, ultrasonication, centrifugation, washing, and drying. The modified interface additive is obtained by mixing ethylene glycol diglycidyl ether, protocatechuic acid and p-toluenesulfonic acid monohydrate, heating and stirring under inert gas protection, reacting at elevated temperature, and then cooling.
2. The high-adhesion epoxy zinc-rich primer according to claim 1, characterized in that, The N-FrGO dispersion is prepared by placing reduced graphene oxide and ammonium fluoride in two separate corundum boats, then inverting the corundum boat containing reduced graphene oxide above the corundum boat containing ammonium fluoride, and then placing them together in the corundum tube of a tubular furnace. After purging the furnace chamber with nitrogen for 20-30 minutes, the temperature is increased to 800-850°C at a rate of 5°C / min under a nitrogen flow rate of 50 mL / min, and the reaction is maintained at this temperature for 30-50 minutes. After cooling to room temperature, N-FrGO is obtained, which is then added to deionized water and stirred for 30-40 minutes, followed by ultrasonic dispersion for 20-30 minutes. The polyaniline dispersion is prepared by adding conductive polyaniline powder to deionized water, stirring for 20-30 minutes, and then ultrasonically dispersing for 20-30 minutes.
3. The high-adhesion epoxy zinc-rich primer according to claim 2, characterized in that, The N-FrGO dispersion comprises the following raw materials in parts by weight: 1-1.2 parts of reduced graphene oxide, 10-12 parts of ammonium fluoride, and 500-600 parts of deionized water; the polyaniline dispersion comprises the following raw materials in parts by weight: 0.06-0.08 parts of conductive polyaniline powder and 180-200 parts of deionized water.
4. The high-adhesion epoxy zinc-rich primer according to claim 1, characterized in that, The modified interface aid is prepared by mixing 18-22 parts by weight of ethylene glycol diglycidyl ether, 2-2.2 parts by weight of protocatechuic acid and 0.2-0.25 parts by weight of p-toluenesulfonic acid monohydrate, stirring at 70-80°C for 30-40 min under nitrogen protection, increasing the temperature to 100-120°C at 2°C / min, continuing the reaction for 4-6 h, and then cooling to room temperature.
5. The high-adhesion epoxy zinc-rich primer according to claim 1, characterized in that, The polyaniline / N-FrGO composite filler is obtained by adding polyaniline dispersion to N-FrGO dispersion, stirring at 75~80℃ for 1~2h, then ultrasonicating for 20~30min, centrifuging, washing with deionized water 3~5 times, and vacuum drying at 50~60℃ for 20~24h.
6. The high-adhesion epoxy zinc-rich primer according to claim 1, characterized in that, The polyaniline / N-FrGO predispersant was obtained by adding 0.4-0.6 parts of polyaniline / N-FrGO composite filler to 3-5 parts of mixed solvent, magnetically stirring for 10-15 minutes, and then ultrasonically dispersing for 20-30 minutes.
7. The high-adhesion epoxy zinc-rich primer according to claim 1, characterized in that, Component A comprises the following raw materials by weight: 90-110 parts of bisphenol A type liquid epoxy resin, 7-9 parts of modified interface additives, 0.8-1.2 parts of dispersant, 0.3-0.5 parts of defoamer, 12-15 parts of mixed solvent, 2-5 parts of fumed silica, and 700-750 parts of zinc powder, and also includes a polyaniline / N-FrGO pre-dispersion composed of 0.4-0.6 parts of polyaniline / N-FrGO composite filler and 3-5 parts of mixed solvent; Component B is 60-75 parts of curing agent; the mixed solvent is a xylene / n-butanol mixed solvent, wherein the mass ratio of xylene to n-butanol in the mixed solvent is 8:2; the curing agent is a polyamide curing agent.
8. The high-adhesion epoxy zinc-rich primer according to claim 1, characterized in that, The mixture is prepared by thoroughly mixing component A and component B and allowing it to mature for 10-20 minutes.
9. The high-adhesion epoxy zinc-rich primer according to claim 1, characterized in that, Component A is prepared by mixing and stirring bisphenol A type liquid epoxy resin and modified interface additives for 10-15 min, adding dispersant, defoamer and mixed solvent and stirring for 15-20 min, then slowly adding polyaniline / N-FrGO pre-dispersion and dispersing at high speed at 1200-1500 rpm for 20-30 min, followed by adding fumed silica and dispersing at high speed at 1200-1500 rpm for 20-30 min; then slowly adding zinc powder in 3-5 portions and dispersing at 1000-1200 rpm for 30-40 min, followed by vacuum degassing.
10. A gradient curing preparation process, characterized in that, The high-adhesion epoxy zinc-rich primer according to any one of claims 1 to 9 is prepared by the following gradient curing process, the steps of which are as follows: the epoxy zinc-rich primer is sprayed onto the surface of Q235 steel plate after sandblasting and rust removal, the dry film thickness is controlled to be 60-80μm, and the plate is allowed to stand and level at 25-30℃ for 30-40min. Then, the back of the sprayed steel plate is heated at 55-60℃ for 1-2h, and then transferred to an oven at 70-80℃ for overall baking for 4-5h, finally obtaining a high-adhesion epoxy zinc-rich paint film.