High-solid epoxy seal primer suitable for wet basal plane and preparation method of high-solid epoxy seal primer

Abstract

The invention relates to the technical field of coatings, discloses a high-solid epoxy seal primer suitable for a wet base surface and a preparation method of the high-solid epoxy seal primer, and aims to overcome the defect of poor application performance of the wet base surface in the prior art. A water-responsive curing system, dynamic interface modification components and a synergistic mechanism of precise cross-linking regulation are constructed, a special curing agent with anti-protonation characteristics is adopted and matched with a modified molecular sieve to adsorb water on a basal plane so as to weaken water interference, interface bonding is enhanced through a coupling agent containing dynamic covalent bonds and a composite filler, and the water-based composite material is prepared. The rheology regulation and control auxiliary agent is supplemented to optimize the construction performance, the environment-friendly component is fused to give consideration to the characteristic of low volatility, efficient curing of a high-water-content base plane is achieved, the interface stability and long-acting protection capacity of a coating and a base material are improved, the coating is suitable for industrial large-scale production, and the coating requirement in a humid environment is met.

Description

Technical Field

[0001] This invention relates to the field of coating technology, and in particular to a high-solids epoxy sealing primer suitable for damp substrates and its preparation method. Background Technology

[0002] High-solids epoxy sealing primers are the base material in industrial anti-corrosion and building protective coating systems. Their core function is to seal the pores of the substrate, prevent the penetration of moisture and harmful substances, and provide a solid adhesion base for subsequent coatings. Due to their environmental advantages of low volatile organic compound emissions, they are in line with the current industry trend of green development and have been widely used in steel structures, bridges, ships, underground engineering and other fields, becoming a key link in ensuring the long-term protective performance of coating systems.

[0003] CN117567918A discloses a production process for a low-VOC, environmentally friendly, high-solids epoxy zinc-rich primer. This process involves adding functional additives—comprising salt spray resistance agents, drying agents, adhesion promoters, and polyamide curing agents with specific structures—to the raw materials. The product is then prepared through a specific process of stirring, mixing, grinding, and filtration. This process improves the primer's salt spray resistance, fast drying performance, adhesion, and solids content. CN115160894A discloses a high-solids, low-surface-treatment, moisture-curing epoxy resin coating, its preparation method, and its application. This coating uses a two-component system: component A (composed of epoxy resin and flexible resin) and component B (composed of modified polyamide and modified aliphatic amine curing agents). Combined with additives such as rust converters and silane coupling agents, this improves the coating's moisture-curing effect under low surface-treatment conditions.

[0004] However, in practical applications, the substrate is often damp or even has a thin water film. The moisture on the damp substrate will preferentially compete with the active hydrogen of the amine curing agent for protonation, consuming the effective curing components. At the same time, the characteristics of the high solids system hinder the rapid escape of moisture. The resulting interfacial water film will shield the epoxy groups from effective collision with the curing agent, leading to insufficient cross-linking reaction of the coating, increased internal porosity, and consequently, a decrease in the physical adsorption and chemical bonding forces between the coating and the substrate. Ultimately, this results in problems such as incomplete curing in the short term, blistering and cracking of the coating in the medium term, and failure of the long-term protective system. Summary of the Invention

[0005] The technical problem to be solved by this invention is that the existing technology has the disadvantage of poor performance on damp substrates. To this end, we propose a high-solids epoxy sealing primer suitable for damp substrates and its preparation method.

[0006] To achieve the above objectives, this application adopts the following technical solution: a high-solids epoxy sealing primer suitable for damp substrates, comprising the following raw materials by weight: 40-44 parts of main resin, 24-26 parts of curing system, 12-14 parts of interface modification component, 8-10 parts of conditioning system and 5-7 parts of protective additive; the main resin comprises 34-38 parts of epoxy-polyurethane block copolymer and 6 parts of amino-terminated polyether modified epoxy resin; the curing system comprises 18-20 parts of cashew nut shell phenol-aminoimidazolium salt curing agent, 4 parts of modified 3A molecular sieve and 2 parts of caprolactam-terminated isophorone diisocyanate; the interface modification component comprises 2-4 parts of Schiff base type silane coupling agent and 10 parts of graphene-nano zinc composite filler.

[0007] Preferably, the epoxy-polyurethane block copolymer is prepared by in-situ polymerization of bisphenol A epoxy resin and isophorone diisocyanate at a mass ratio of 9:1, and the epoxy equivalent of the epoxy-polyurethane block copolymer is 220-230 g / eq.

[0008] Preferably, the amino-terminated polyether modified epoxy resin is prepared by a ring-opening reaction of polyetheramine D230 and E-51 epoxy resin at a mass ratio of 1:4, and the molecular weight of the amino-terminated polyether modified epoxy resin is 800-1000.

[0009] Preferably, the cashew phenol-aminoimidazolium salt curing agent is prepared by recrystallizing cashew phenol, 2-methylimidazolium and hexadecane in a mass ratio of 5:2:3 from ethanol and vacuum drying. The cashew phenol-aminoimidazolium salt curing agent has an amine value of 180-200 mgKOH / g and an amine hydrogen equivalent of 280-310 g / eq.

[0010] Preferably, the modified 3A molecular sieve is 3A molecular sieve raw powder modified with silane coupling agent KH-560, with a grafting rate ≥85%.

[0011] Preferably, the Schiff base silane coupling agent is prepared by vacuum distillation purification of silane coupling agent KH-550 and salicylaldehyde in a molar ratio of 1:1.05, and the Schiff base silane coupling agent contains dynamic C=N bonds and siloxane groups.

[0012] Preferably, the control system comprises 3 parts urea-formaldehyde resin modified bentonite, 1 part polyether modified polysiloxane defoamer, and 4-6 parts methylcyclohexyl glycidyl ether, and the protective additives comprise 2-3 parts hindered amine light stabilizer and 3-4 parts organophosphonate rust inhibitor.

[0013] A method for preparing a high-solids epoxy sealing primer suitable for damp substrates includes the following steps: S1: Add the main resin to a mixing tank, heat it, add the interface modification component, and disperse it at high speed until the system is uniform to obtain a basic mixed system; S2: Add the curing system to a dispersion tank, keep it warm and stir to obtain a uniform curing agent premix; S3: Add urea-formaldehyde resin modified bentonite, polyether modified polysiloxane defoamer, methylcyclohexyl glycidyl ether, hindered amine light stabilizer, and organophosphonate rust inhibitor to the basic mixed system in sequence, and stir until the system is uniform and free of bubbles; S4: Filter the mixture in S3 under pressure to obtain a filtrate, mix the filtrate with the curing agent premix, stir evenly, and obtain the finished product.

[0014] Preferably, the amine hydrogen equivalent in the curing agent premix liquid in S2 is controlled at 270-290 g / eq.

[0015] Preferably, the mass ratio of filtrate to curing agent premix in S4 is 3:1, and the stirring speed during mixing is 400-600 r / min, and the stirring time is 4-6 min.

[0016] The technical effects and advantages of this invention are as follows:

[0017] This invention employs a synergistic technical solution that integrates a moisture-responsive curing system, dynamic interface modification components, and precise crosslinking control. Leveraging the anti-protonation properties of the cashew phenol-aminoimidazolium salt curing agent, combined with the active water absorption function of modified 3A molecular sieves, dual moisture control is achieved. The dynamic covalent bonds of the Schiff base silane coupling agent and the interface strengthening effect of the graphene nano-zinc composite filler are combined to construct an interface mechanism integrating chemical anchoring, physical shielding, and dynamic repair. Simultaneously, precise matching of the epoxy amine curing equivalence ratio ensures sufficient crosslinking. With intelligent rheological control and low-VOC formulation design, efficient curing on high-moisture substrates is ultimately achieved. This improves the adhesion and interface stability of the coating to the substrate in humid environments, extends the long-term protective life of the coating, and maintains the environmental advantages of high solids content and low volatile organic compound emissions. This effectively solves the problems of insufficient curing, inadequate adhesion, and poor long-term protective performance in existing technologies applied to humid substrates. Attached Figure Description

[0018] The disclosure of this invention is illustrated with reference to the accompanying drawings. It should be understood that the drawings are for illustrative purposes only and are not intended to limit the scope of protection of this invention. In the drawings, the same reference numerals are used to refer to the same parts:

[0019] Figure 1 This is a flowchart illustrating the preparation process of the high-solids epoxy sealing primer of the present invention. Detailed Implementation

[0020] It is readily understood that, based on the technical solution of this invention, those skilled in the art can propose various interchangeable structural methods and implementations without altering the essential spirit of the invention. Therefore, the following detailed embodiments and accompanying drawings are merely illustrative examples of the technical solution of this invention and should not be considered as the entirety of the invention or as limitations or restrictions on the technical solution of this invention.

[0021] This invention provides a technical solution: a high-solids epoxy sealing primer suitable for damp substrates, comprising five major systems: main resin, curing system, interface modifying components, regulating system, and protective additives. The raw materials of each system are shown in Table 1 below.

[0022]

[0023]

[0024] Table 1

[0025] The main resin serves as the basis for the cross-linking and film formation of the coating, comprising 34-38 parts of epoxy-polyurethane block copolymer and 6 parts of amino-terminated polyether modified epoxy resin;

[0026] Among them, the epoxy-polyurethane block copolymer is prepared by in-situ polymerization of bisphenol A epoxy resin and isophorone diisocyanate at a mass ratio of 9:1, with an epoxy equivalent of 220-230 g / eq. The hydrophobic urea group structure introduced into its molecular chain can reduce the system's sensitivity to moisture while retaining sufficient epoxy active sites.

[0027] The amino-terminated polyether modified epoxy resin is prepared by ring-opening reaction of polyether amine D230 and E-51 epoxy resin at a mass ratio of 1:4. The molecular weight is 800-1000. The flexible polyether segment can relieve curing shrinkage stress, and the primary amino functional group can participate in the cross-linking reaction.

[0028] The curing system performs efficient curing and moisture control functions in humid environments, including 18-20 parts of cashew phenol-aminoimidazolium salt curing agent, 4 parts of modified 3A molecular sieve, and 2 parts of caprolactam-terminated isophorone diisocyanate.

[0029] The cashew phenol-aminoimidazol salt curing agent is prepared by reacting cashew phenol, 2-methylimidazol and hexadecane in a mass ratio of 5:2:3 at 120℃ for 4 hours, followed by recrystallization from ethanol and vacuum drying. It has an amine value of 180-200 mgKOH / g and an amine hydrogen equivalent of 280-310 g / eq. The long-chain alkyl groups form a hydrophobic barrier, and the imidazol salt groups inhibit the protonation of the amine matrix.

[0030] The modified 3A molecular sieve is made by modifying 3A molecular sieve powder with KH-560, with a grafting rate of ≥85%, and can actively capture free water on the basal surface and in the system;

[0031] Caprolactam-terminated isophorone diisocyanate, as an auxiliary crosslinking agent, is stable at room temperature and can unblock and release NCO groups under humid conditions, crosslinking with amine and hydroxyl groups to form a dense network and fill the gaps in the main curing reaction.

[0032] The interface modification component is responsible for strengthening the interfacial bonding between the coating and the substrate and improving the protective performance, including 2-4 parts of Schiff base silane coupling agent and 10 parts of graphene-nano zinc composite filler.

[0033] Schiff base type silane coupling agent is prepared by reacting 3-aminopropyltriethoxysilane and salicylaldehyde at a molar ratio of 1:1.05 at 70±2℃ for 2h, followed by vacuum distillation purification. The purity is ≥95% and the residual water content is ≤0.5%. It contains dynamic C=N bonds and siloxane groups. The siloxane groups condense with the hydroxyl groups of the substrate to form chemical anchors. The C=N bonds can repair interfacial microcracks.

[0034] The graphene-nano zinc composite filler is made by compounding graphene sheets and nano zinc powder in a certain proportion and then modifying it with perfluorooctyltriethoxysilane. The surface hydrophobic angle is ≥110°. The graphene sheets form a physical barrier, and the nano zinc powder plays a cathodic protection role.

[0035] The control system is used to balance the construction performance and film-forming quality of the high-solids system, including 3 parts urea-formaldehyde resin modified bentonite, 1 part polyether modified polysiloxane defoamer and 4-6 parts methylcyclohexyl glycidyl ether.

[0036] Urea-formaldehyde resin modified bentonite is a finished product of 828 type organic bentonite grafted with urea-formaldehyde resin prepolymer. It has an oil absorption value of ≥25ml / 100g, high shear reduces viscosity to ensure leveling, and low shear forms a three-dimensional network to avoid sagging.

[0037] Polyether-modified polysiloxane defoamers combine compatibility and defoaming efficiency, and can quickly eliminate bubbles generated during dispersion.

[0038] Methylcyclohexyl glycidyl ether, as a low-volatility diluent, does not introduce hydrophilic groups, can reduce the viscosity of the system, and participate in cross-linking reactions.

[0039] Protective additives are used to improve the long-term aging resistance and rust prevention performance of coatings, including 2-3 parts hindered amine light stabilizer and 3-4 parts organophosphonate rust inhibitor;

[0040] Hindered amine light stabilizers contain 2,2,6,6-tetramethylpiperidinyl functional groups, which can capture free radicals during the aging process and inhibit coating degradation;

[0041] Organophosphonate rust inhibitors contain phosphonate groups (-PO(OH)2), which can complex with metal ions to form a passivation film and synergistically enhance the rust prevention effect with nano zinc powder.

[0042] This invention also provides a method for preparing a high-solids epoxy sealing primer suitable for damp substrates. The process steps and parameter settings are described in detail below through specific embodiments.

[0043] Example 1

[0044] This embodiment provides a method for preparing a high-solids epoxy sealing primer suitable for damp substrates, specifically including the following steps:

[0045] S1: Mixing the main resin with the interface modification component

[0046] 36 parts of epoxy-polyurethane block copolymer and 6 parts of amino-terminated polyether modified epoxy resin were added sequentially to the stirred tank. Mechanical stirring was started, and the speed was adjusted to 800 r / min. The temperature was raised to 75℃ and stirred for 15 min to ensure complete fusion of the two resins. Subsequently, 3 parts of Schiff base silane coupling agent and 10 parts of graphene-nano zinc composite filler were added. The stirring speed was increased to 3200 r / min and high-speed dispersion was carried out for 60 min. The particle size of the system was checked every 15 min during the process.

[0047] It is important to note that the resin mixing temperature should be controlled between 70-80℃. When the temperature is below 70℃, the compatibility between the epoxy-polyurethane block copolymer and the amino-terminated polyether modified epoxy resin decreases, and the stirring time needs to be extended to more than 20 minutes to achieve uniform fusion. When the temperature is above 80℃, the hydrolysis rate of C=N bonds in the Schiff base silane coupling agent increases, which leads to a decrease in the dynamic interface repair function.

[0048] S2: Premixed curing system

[0049] 19 parts of cashew phenol-aminoimidazolium salt curing agent, 4 parts of modified 3A molecular sieve, and 2 parts of caprolactam-terminated isophorone diisocyanate were added sequentially to the dispersion vessel. The temperature was raised to 45°C, the rotation speed was adjusted to 800 r / min, and the mixture was kept warm and stirred for 20 min to obtain a homogeneous curing agent premix. The amine hydrogen equivalent was determined by titration.

[0050] It is important to note that the premixing temperature should be controlled between 40-50℃. When the temperature is below 40℃, the dispersibility of the modified 3A molecular sieve in the curing agent decreases and the water absorption efficiency decreases by 20%. When the temperature is above 50℃, the capping rate of caprolactam-terminated isophorone diisocyanate decreases, and the prematurely uncapped NCO groups will react with the amine groups to form urea bonds, resulting in a sharp increase in the viscosity of the premix.

[0051] The amine hydrogen equivalent should be controlled between 270-290 g / eq. When the equivalent is <270 g / eq, the curing agent is excessive, and the impact strength of the coating will decrease after curing. When the equivalent is >290 g / eq, the curing agent is insufficient, which will lead to a decrease in crosslinking density.

[0052] S3: Add regulatory system and protective additives

[0053] The mixture obtained in S1 was naturally cooled to 35°C. While maintaining a stirring speed of 800 r / min, 3 parts of urea-formaldehyde resin modified bentonite, 1 part of polyether modified polysiloxane defoamer, 5 parts of methylcyclohexyl glycidyl ether, 2.5 parts of hindered amine light stabilizer, and 3.5 parts of organophosphonate rust inhibitor were added sequentially. After each addition, the mixture was stirred for 5 min. After all the ingredients were added, the stirring speed was adjusted to 600 r / min, and the mixture was kept warm and stirred for 30 min to obtain a homogeneous, bubble-free mixture.

[0054] It should be noted that the theoretical temperature range of the system is 32-38℃. When the temperature is <32℃, the activity of the urea-formaldehyde resin modified bentonite molecular chain decreases, making it difficult to form a stable and reversible three-dimensional network. When the temperature is >38℃, the hydrolysis rate of Schiff base silane coupling agent increases. At the same time, the amine groups in the curing agent premix are prone to react with the epoxy groups in advance, resulting in a shortened pot life after subsequent mixing.

[0055] It is important to note that the order in which the reagents are added in this step cannot be adjusted. First, the basic rheological network is constructed using a thixotropic agent, then the defoamer is used to eliminate the air bubbles introduced during the initial dispersion, and finally the diluent and protective agent are added. This avoids premature reaction between the protective agent and the interface modification components, and also adjusts the viscosity to the application range using the diluent.

[0056] S4: Finished Product Preparation and Mixing

[0057] Turn off the heating device of the mixing tank and allow it to cool naturally to 25°C. Use a 200-mesh nylon filter to filter the mixing system under pressure of 0.3MPa to remove large particles and agglomerates, and collect the filtrate. Before construction, mix the filtrate and the premixed curing agent at a mass ratio of 3:1, turn on the stirring device, adjust the speed to 500r / min, stir for 5min, and after mixing evenly, obtain a high-solids epoxy sealing primer.

[0058] Example 2

[0059] This embodiment provides a method for preparing a high-solids epoxy sealing primer suitable for damp substrates, which differs from Example 1 in that:

[0060] The amount of Schiff base type silane coupling agent used was 2 parts, and the selection, ratio and preparation method of the other raw materials were the same as in Example 1.

[0061] This embodiment aims to verify the effect of reducing the amount of Schiff base silane coupling agent on the coating interface adhesion and dynamic repair performance.

[0062] Example 3

[0063] This embodiment provides a method for preparing a high-solids epoxy sealing primer suitable for damp substrates, which differs from Example 1 in that:

[0064] The amount of Schiff base type silane coupling agent used was 4 parts, and the selection, ratio and preparation method of the other raw materials were the same as in Example 1.

[0065] This embodiment aims to verify whether there is a problem of over-coating leading to blockage of carrier pores when the amount of Schiff base silane coupling agent is increased.

[0066] Example 4

[0067] This embodiment provides a method for preparing a high-solids epoxy sealing primer suitable for damp substrates, which differs from Example 1 in that:

[0068] The grafting rate of the modified 3A molecular sieve was 85%, and the selection, proportioning and preparation methods of the remaining raw materials were the same as those in Example 1.

[0069] This embodiment aims to verify the effect of a decrease in the grafting rate of the moisture trapping agent on the moisture adsorption capacity and curing effect.

[0070] Example 5

[0071] This embodiment provides a method for preparing a high-solids epoxy sealing primer suitable for damp substrates, which differs from Example 1 in that:

[0072] The amount of methylcyclohexyl glycidyl ether used was 4 parts, and the selection, ratio and preparation method of the other raw materials were the same as in Example 1.

[0073] This embodiment aims to verify the effect of decreasing the amount of reactive diluent on the system viscosity and workability.

[0074] Comparative Example 1

[0075] Using the technical solution with publication number CN117567918A, weigh out 35 parts of epoxy resin, 10 parts of zinc powder, 5 parts of organic bentonite, 6 parts of anti-rust pigment, 4 parts of reactive diluent, 3 parts of dispersant, 5 parts of thickener, 5 parts of silane coupling agent, 5 parts of leveling agent, 8 parts of defoamer, 10 parts of functional additives, and 24 parts of environmentally friendly solvent.

[0076] First, epoxy resin, zinc powder, organic bentonite, rust-preventive pigment, reactive diluent, and environmentally friendly solvent are added to a reaction vessel and stirred at 1200 rpm for 45 minutes at a reaction temperature of 50°C. Then, dispersant, thickener, silane coupling agent, leveling agent, and defoamer are added and stirred at 1300 rpm for 28 minutes at a reaction temperature of 60°C. Functional additives are added while stirring, and after mixing evenly, the mixture is ground and filtered to obtain the product.

[0077] Comparative Example 2

[0078] This comparative example provides a method for preparing a high-solids epoxy sealing primer suitable for damp substrates, which differs from Example 1 in that:

[0079] The Schiff base silane coupling agent was replaced with an equal mass of 3-aminopropyltriethoxysilane, which was not condensed with salicylaldehyde. The selection, proportioning and preparation methods of the remaining raw materials were the same as in Example 1.

[0080] This comparative example aims to verify the effect of Schiff base silane coupling agents on the interfacial adhesion and dynamic repair performance of coatings.

[0081] Comparative Example 3

[0082] This comparative example provides a method for preparing a high-solids epoxy sealing primer suitable for damp substrates, which differs from Example 1 in that:

[0083] The modified 3A molecular sieve was replaced with an equal mass of unmodified 3A molecular sieve, with a grafting rate of 40%. The selection, proportioning and preparation methods of the remaining raw materials were the same as in Example 1.

[0084] This comparative example aims to verify the effect of high grafting rate modified 3A molecular sieve on water adsorption capacity and curing effect in humid environments.

[0085] Comparative Example 4

[0086] This comparative example provides a method for preparing a high-solids epoxy sealing primer suitable for damp substrates, which differs from Example 1 in that:

[0087] The cashew phenol-aminoimidazolium salt curing agent was replaced with an equal mass of polyamide 650 curing agent, and the selection, proportioning and preparation methods of the remaining raw materials were the same as in Example 1.

[0088] This comparative example aims to verify the effect of cashew phenol-aminoimidazolium salt curing agent on inhibiting protonation reaction and curing efficiency in humid environments.

[0089] To verify the performance of the high-solids epoxy sealing primer for damp substrates provided by this invention, systematic tests were conducted on the catalysts prepared by the methods of Examples 1-5 and Comparative Examples 1-4, focusing on substrate compatibility, interface stability, curing performance, long-term protective performance, environmental protection and construction performance. The specific test plan is as follows.

[0090] Test Example 1

[0091] Referring to GB / T 5210-2006 "Adhesion Test of Paints and Varnishes by Pull-Off Method", concrete and Q235 steel test blocks were cured for 24 hours at 25℃ and 85% relative humidity, forming a thin water film on the surface, which served as the wet test substrate. The test object was uniformly coated on the wet substrate, and after curing for 12 hours, the peel strength (unit: MPa) of the coating to the wet concrete substrate and the wet Q235 steel substrate was measured using a pull-out tester. Referring to the water absorption rate determination method in the industry standard SY / T 0447-1996 "Technical Standard for External Anticorrosion Coating of Coal Tar Enamelled Coating for Buried Steel Pipelines", and combined with the water absorption rate performance requirements of epoxy primers in GB / T 22374-2018 "Construction Primers", the test object was dried to constant weight and weighed, then immersed in distilled water for 24 hours, removed, wiped dry, and weighed again to calculate the coating water absorption rate (unit: %). After curing for 12 hours, according to GB / T According to 1766-2008 "Rating Method for Aging of Paint and Varnish Coatings", the coating surface is visually inspected for defects such as blistering, pinholes, and wrinkling. If there are no defects, it is considered qualified. The specific test results are shown in Table 2.

[0092]

[0093] Table 2

[0094] According to the data in Table 2, in Example 1, the 3 parts of Schiff base-type silane coupling agent can fully form chemical anchors with the hydroxyl groups of the substrate. The modified 3A molecular sieve with a grafting rate of ≥85% efficiently adsorbs free moisture on the substrate surface. Combined with the cashew phenol-aminoimidazolium salt curing agent to inhibit amine matrix protonation, the pull-out adhesion is optimized and the coating water absorption rate is minimized. In Example 2, due to the reduced Schiff base dosage, the number of chemical anchors decreased, resulting in a 17%-19% decrease in adhesion and an increase in water absorption rate to 1.5%. In Example 3, the Schiff base was excessive, only slightly coating the filler, but the performance was still better than that of Example 2. In Example 4, the grafting rate of the modified 3A molecular sieve decreased to 85%. The reduced moisture capture efficiency led to a slight increase in water absorption. In Example 5, the reduced amount of methylcyclohexyl glycidyl ether increased the system viscosity, resulting in uneven filler dispersion and making it the group with the worst adhesion and water absorption among the examples. Comparative Example 1 had an adhesion of only 60% of that of Example 1 and a water absorption rate of 3.5%. Comparative Example 2 used ordinary 3-aminopropyltriethoxysilane instead of Schiff base, which lacked dynamic repair function and caused interface blistering. Comparative Example 3 showed that the unmodified molecular sieve failed to capture moisture, resulting in more obvious blistering. Comparative Example 4 showed that the polyamide 650 curing agent lacked anti-protonation ability, and the effective curing components were missing, resulting in severe blistering and a water absorption rate of 4.2%.

[0095] Test Example 2

[0096] Referring to GB / T 1740-2007 "Determination of Damp Heat Resistance of Paint Films" and GB / T 5210-2006 "Pull-off Adhesion Test of Paints and Varnishes", the cured coating was placed in a constant temperature and humidity chamber, with the temperature set at 47±1℃ and relative humidity at 96%±2%, and aged continuously for 1000h. After aging, the test block was removed, the pull-off adhesion was measured, and the adhesion retention rate after immersion was calculated (unit: %). Referring to the temperature cycling test provisions in GB / T 2423.3-2016 "Environmental Testing Part 2: Test Methods, Cab: Constant Damp Heat Test", the cured coating was placed in a temperature cycling chamber, kept at -20℃ for 8h, then heated to 40℃ for 8h, and subjected to 5 cycles of hot and cold. After returning to room temperature, the adhesion after hot and cold cycling was measured (unit: MPa). The specific test results are shown in Table 3.

[0097]

[0098] Table 3

[0099] According to the data in Table 3, in Example 1, the C=N bond of the Schiff base can repair the interfacial microcracks caused by immersion and thermal cycling through breakage and recombination. The graphene sheets block water intrusion, making the adhesion retention rate after immersion and the adhesion after thermal cycling close to the initial value. In Example 2, the Schiff base dosage was insufficient, the repair sites decreased, the retention rate dropped to 91.5%, and the adhesion decreased by 16.7% after cycling. In Example 3, the Schiff base dosage was excessive but did not damage the repair function, and the performance was still better than that of Example 2. In Example 4, the grafting rate of the modified 3A molecular sieve decreased, resulting in slight water residue and easy formation of cracks at the interface. The retention rate dropped slightly to 92.3% in Example 5 due to insufficient active diluent and uneven dispersion, resulting in interface stress concentration and the lowest retention rate and post-cycle adhesion among the examples. Comparative Example 1 had no dynamic repair and barrier function, with a retention rate of only 77.3% and post-cycle adhesion less than 50% of Example 1. Comparative Example 2 had no Schiff base, and the interface cracks continued to expand, causing the retention rate to plummet to 66.8%. Comparative Examples 3-4 had loose interface structures due to residual moisture or insufficient curing, resulting in retention rates as low as 60.7%-63.5% and post-cycle adhesion of only 1.0-1.1 MPa.

[0100] Test Example 3

[0101] Referring to GB / T 1728-2020 "Determination of Drying Time of Paint Film and Putty Film", the surface drying time (unit: h) of the sample in a humid environment was determined using the cotton ball blowing method. Similarly, the actual drying time (unit: h) of the sample with a non-stick filter paper coating in a humid environment was determined using the filter paper pressing method. According to GB / T 1730-2007 "Determination of Hardness of Paint Film - Pendulum Damping Test", the swelling method was used, where the sample was immersed in toluene for 24 hours, the degree of swelling was measured, and the crosslinking density (unit: ×10⁻¹⁰) was calculated. -4 mol / cm 3(See Table 4 for details).

[0102]

[0103] Table 4

[0104] According to the data in Table 4, in Example 1, the imidazole salt group of the cashew phenol-aminoimidazolium salt curing agent shields the protonation attack of moisture on the amino groups, and the high grafting rate of the modified 3A molecular sieve quickly removes moisture from the system, resulting in the fastest surface drying and solid drying, and the highest crosslinking density. In Example 2, insufficient Schiff base led to a slight increase in interfacial moisture, a decrease in the epoxy-amine reaction rate, slower surface drying and solid drying than in Example 1, and a 7.9% decrease in crosslinking density. In Example 4, the reduced grafting rate of the modified 3A molecular sieve and the decreased moisture removal efficiency prolonged the curing induction period. In Example 5, insufficient reactive diluent... The diffusion of epoxy groups was hindered, resulting in the slowest surface drying and complete drying, and the lowest crosslinking density. In Comparative Example 1, the moisture-free responsive system showed that moisture preferentially reacted with amine groups, with surface drying being twice that of Example 1, complete drying being nearly twice that of Example 1, and crosslinking density only 57.9% of Example 1. In Comparative Example 4, the polyamide 650 curing agent had no anti-protonation ability, and the active hydrogen was completely protonated, causing the curing reaction to stagnate. Surface drying and complete drying reached their peak values, and the crosslinking density was less than 50% of Example 1. In Comparative Examples 2-3, due to the lack of a single component, moisture continuously interfered with curing, and the performance was between that of Comparative Examples 1 and 4.

[0105] Test Example 4

[0106] Referring to GB / T 1771-2007 "Determination of Resistance to Neutral Salt Spray of Paints and Varnishes", a scratch was made along the length of the test block using a utility knife, penetrating the coating to the substrate. The coated test block was then placed in a salt spray test chamber and continuously sprayed with 5% NaCl solution for 1500 hours. The appearance of the coating was observed, and the salt spray resistance was tested. Referring to GB / T 30786-2014 "Guidelines for Scratch Marking of Metal Plate Coatings for Corrosion Testing of Paints and Varnishes", the temperature was set at 47±1℃ and the relative humidity at 96%±2%, and the aging was continued for 1000 hours. After aging, the test block was removed, and the adhesion retention rate under damp heat aging was measured (unit: %). Referring to GB / T 1740-2007 "Determination of Resistance to Damp Heat of Paint Film", after the salt spray test, the rust expansion width at the scratch was measured (unit: mm), as shown in Table 5.

[0107]

[0108] Table 5

[0109] As shown in Table 5, in Example 1, graphene sheets were stacked to form a dense barrier layer, preventing Cl from forming. -In Example 1, moisture penetration was observed; nano-zinc powder released electrons to achieve cathodic protection; Schiff base repaired interfacial microcracks, thus exhibiting no blistering or discoloration after 1500 hours of salt spray resistance, the highest adhesion retention rate during wet heat aging, and the narrowest scratch corrosion width. In Example 2, insufficient Schiff base led to inadequate repair of interfacial cracks, slight intrusion of corrosive media, a decrease in wet heat retention rate to 88.7%, and an increase in scratch corrosion width of 37.5%. In Example 5, insufficient reactive diluent resulted in localized gaps in the graphene barrier, causing slight discoloration; the wet heat retention rate and scratch corrosion width were the worst among the examples, but still superior. Compared with the comparative examples; Comparative Example 1 had no composite filler protection, and the resin swelled, resulting in slight blistering. The wet heat retention rate was only 78% of that of Example 1, and the scratch and rust width was 3.25 times greater; Comparative Example 2 had no Schiff base, and the interface cracks expanded, resulting in large-area peeling. The wet heat retention rate dropped to 65.3%; Comparative Example 3 had no modified molecular sieve, which could not remove moisture. The coating porosity was high, and the protective performance was close to that of Comparative Example 2; Comparative Example 4 had insufficient curing, resulting in dense micropores in the coating. The corrosive medium directly contacted the substrate, resulting in complete peeling. The wet heat retention rate and scratch and rust width were the worst.

[0110] Test Example 5

[0111] Referring to GB / T 1725-2007 "Determination of Non-volatile Content in Paints, Varnishes and Plastics", the test object was dried in a constant temperature oven at 105℃ for 3 hours, cooled to room temperature, and accurately weighed to calculate the solid content (unit: %). Referring to GB / T 23986-2009 "Determination of Volatile Organic Compound Content in Paints and Varnishes - Gas Chromatography", the volatile organic compound content in the sample was determined by gas chromatography (unit: g / L). Referring to GB / T 1723-1993 "Determination of Viscosity of Coatings", the application viscosity of the sample was determined by a rotational viscometer (unit: mPa·s), as shown in Table 6.

[0112]

[0113] Table 6

[0114] According to the data in Table 6, Example 1 showed the best construction viscosity. In Examples 2-4, the viscosity was less affected by changes in the amount of Schiff base or the grafting rate of molecular sieve, and the viscosity was between 950-990 mPa·s, indicating good workability. In Example 5, the active diluent was reduced to 4 parts, and the system viscosity increased to 1020 mPa·s, which still met the construction requirements. In Comparative Examples 2-4, due to the absence of Schiff base or high grafting rate molecular sieve, the compatibility of system components decreased, and the construction viscosity increased to 1050-1100 mPa·s. In addition, the trace residual volatiles of the missing components increased the VOC to 126-130 g / L, and the environmental protection and construction adaptability were not as good as the present invention.

[0115] The technical scope of this invention is not limited to the content described above. Those skilled in the art can make various modifications and variations to the above embodiments without departing from the technical concept of this invention, and all such modifications and variations should fall within the protection scope of this invention.

Claims

1. A high solids, epoxy-based seal primer suitable for use on damp substrates, characterized in that, The method comprises the following raw materials by weight: 40-44 parts of main resin, 24-26 parts of curing system, 12-14 parts of interface modification component, 8-10 parts of regulation system and 5-7 parts of protective additive; The main resin comprises 34-38 parts of epoxy-polyurethane block copolymer and 6 parts of amino-terminated polyether modified epoxy resin; The curing system comprises 18-20 parts of cardanol-aminimidazole salt curing agent, 4 parts of modified 3A molecular sieve and 2 parts of caprolactam-terminated isophorone diisocyanate; The interface modification component comprises 2-4 parts of Schiff base type silane coupling agent and 10 parts of graphene-nano zinc composite filler.

2. A high solids, epoxy-based seal primer suitable for use on damp substrates according to claim 1, characterized in that: The epoxy-polyurethane block copolymer is prepared by in-situ polymerization of bisphenol A epoxy resin and isophorone diisocyanate at a mass ratio of 9:1, and the epoxy equivalent weight of the epoxy-polyurethane block copolymer is 220-230 g / eq.

3. A high solids, epoxy-based seal primer suitable for use on damp substrates according to claim 1, characterized in that: The amino-terminated polyether modified epoxy resin is prepared by ring-opening reaction of polyether amine D230 and E-51 epoxy resin at a mass ratio of 1:4, and the molecular weight of the amino-terminated polyether modified epoxy resin is 800-1000.

4. A high solids, epoxy-based seal primer suitable for use on damp substrates according to claim 1, characterized in that: The cardanol-aminimidazole salt curing agent is prepared by ethanol recrystallization and vacuum drying of cardanol, 2-methyl imidazole and chlorohexadecane at a mass ratio of 5:2:3, and the amine value of the cardanol-aminimidazole salt curing agent is 180-200 mgKOH / g, and the amine hydrogen equivalent is 280-310 g / eq.

5. A high solids, epoxy-based seal primer suitable for use on damp substrates according to claim 1, characterized in that: The modified 3A molecular sieve is a 3A molecular sieve raw powder modified by silane coupling agent KH-560, and the grafting rate is ≥85%.

6. A high solids, epoxy-based seal primer suitable for use on damp substrates according to claim 1, characterized in that: The Schiff base type silane coupling agent is prepared by vacuum distillation purification of silane coupling agent KH-550 and salicylaldehyde at a molar ratio of 1:1.05, and the Schiff base type silane coupling agent contains dynamic C=N bond and siloxane group.

7. A high solids, epoxy-based seal primer suitable for use on damp substrates according to claim 1, wherein: The regulation system comprises 3 parts of urea-formaldehyde resin modified bentonite, 1 part of polyether modified polysiloxane defoaming agent and 4-6 parts of methylcyclohexyl glycidyl ether, and the protective additive comprises 2-3 parts of hindered amine light stabilizer and 3-4 parts of organic phosphonate anti-rust agent.

8. A process for the preparation of a high solids, moisture tolerant, epoxy-based seal primer, characterized in that, The method comprises the following steps: S1: adding the main resin into a stirred tank, adding the interface modification component after warming, and dispersing at high speed until the system is uniform to obtain a basic mixed system; S2: adding the curing system into a dispersion tank, and stirring under heat to obtain a uniform curing agent premix; S3: sequentially adding urea-formaldehyde resin modified bentonite, polyether modified polysiloxane defoaming agent, methylcyclohexyl glycidyl ether, hindered amine light stabilizer and organic phosphonate anti-rust agent into the basic mixed system in order, and stirring until the system is uniform and bubble-free; S4: pressurizing and filtering the mixed system in S3 to obtain a filtrate, mixing the filtrate with the curing agent premix, and stirring uniformly to obtain a finished product.

9. The method of making a high solids, moisture tolerant, epoxy primer sealer according to claim 8, wherein: The amine hydrogen equivalent of the curing agent premix in S2 is controlled at 270-290 g / eq.

10. The method of making a high solids, moisture tolerant, epoxy primer sealer of claim 8, wherein: The mass ratio of the filtrate to the curing agent premix in S4 is 3:1, the stirring speed is 400-600 r / min during mixing, and the stirring time is 4-6 min.

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