A low-density epoxy primer strongly attached to a class H flash rust surface and a preparation method thereof

Abstract

The application discloses a low-density epoxy primer with strong adhesion to H-grade flash rust surface and a preparation method thereof, and relates to the field of paint chemical industry. The epoxy primer comprises an A component and a B component. The A component comprises an epoxy resin, double-layer coated hollow glass microbeads, a thixotropic agent, a wetting dispersant, pigments, barium sulfate, talcum powder, a solvent A, a defoaming agent, a first silane coupling agent and an aluminum paste. The B component comprises a curing agent, an accelerator and a solvent B. The low-density epoxy primer with strong adhesion to H-grade flash rust surface has excellent adhesion and excellent corrosion resistance on the surface of a metal substrate treated by manual rust removal, mechanical rust removal, water sand blasting rust removal and the like, has high tolerance to flash rust on the surface treated by water sand blasting rust removal, and can be suitable for H-grade flash rust surface.

Description

Technical Field

[0001] This invention relates to the field of paint chemicals, and more specifically, to a low-density epoxy primer with strong adhesion to H-grade flash rust surfaces and its preparation method. Background Technology

[0002] Steel components, as a metallic material, are widely used in various fields such as construction, manufacturing, transportation, and aerospace. They are also a core material in modern shipbuilding, mainly used in the manufacture of ship hull structures, equipment, and components. Before leaving the factory, steel components are generally coated with shop primer or clear grease. However, the protective period of shop primer or clear grease is about 3 to 6 months, while the construction cycle of steel components is long and internal corrosion is severe. Therefore, rust removal is necessary for steel structures.

[0003] Among numerous rust removal methods, high-pressure water blasting is dust-free and cost-effective, thus gradually becoming the mainstream choice in the rust removal field due to its economic, efficient, and environmentally friendly characteristics. After high-pressure water blasting, steel components exposed to air will experience varying degrees of flash rust due to moisture or corrosive substances. Flash rust is classified into L-level (light), M-level (medium), and H-level (severe), with H-level being the most severe. H-level severe flash rust is characterized by severe corrosion, appearing as a dark reddish-yellow or brown rust layer on the original steel surface. The rust layer is thick, loosely attached, evenly distributed, and appears in patches. Light wiping with a cloth reveals obvious rust marks. H-level flash rust severely affects coating adhesion, leading to coating peeling or blistering. The corrosion weakens the metal's corrosion resistance, shortens its service life, affects surface appearance, and reduces product value.

[0004] Chinese patent CN109370380A discloses a high-solids anti-corrosion coating for rust-prone surfaces and its preparation method, primarily focusing on environmentally friendly coatings that do not cause pollution. Chinese patent CN103788829A discloses a heavy-duty anti-corrosion epoxy primer for low-grade substrate treatment, applicable to rust-prone and damp low-grade steel substrates. Chinese patent CN103725159A discloses a highly adaptable anti-corrosion coating that exhibits good adhesion to hot-dip galvanized steel, rust-prone hot-dip galvanized steel, corroded steel, and conventional coatings using epoxy, acrylic, or fluorocarbon resins as film-forming materials, and possesses excellent anti-corrosion, weather resistance, and media resistance properties. Chinese patent CN113321987A discloses a high-tolerance epoxy primer for water-jet rust removal surfaces, its preparation method, and its applications. This primer is suitable for steel structures with moderate or mild flash rust surfaces after water-jet rust removal treatment and residual corrosion inhibitors. The coatings mentioned in the above patents each have their own advantages, but none of them are suitable for H-grade flash rust surfaces.

[0005] There are no reports in the current technology regarding the formation of new flash rust on high-pressure water-blasted surfaces, with a flash rust grade of H. Existing epoxy primers with low surface treatment only achieve salt spray resistance of 1000-1400 hours, which is still far from the high salt spray resistance requirement of over 5000 hours required for heavy-duty anti-corrosion applications in shipbuilding and marine engineering. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a low-density epoxy primer with strong adhesion to H-grade flash rust surfaces and its preparation method. The low-density epoxy primer of this invention exhibits excellent adhesion and superior corrosion resistance on metal substrates treated by manual rust removal, mechanical rust removal, and water blasting. It also demonstrates high tolerance for flash rust on water blasting treated surfaces and is suitable for H-grade flash rust surfaces.

[0007] One of the objectives of this invention is to provide a low-density epoxy primer that exhibits strong adhesion to H-grade flash rust surfaces.

[0008] The low-density epoxy primer with strong adhesion to H-grade flash rust surfaces described in this invention is prepared from raw materials comprising the following components:

[0009] Component A and Component B;

[0010] Component A includes epoxy resin, double-layer coated hollow glass microspheres, thixotropic agent, wetting and dispersing agent, pigment, barium sulfate, talc, solvent A, defoamer, first silane coupling agent and aluminum powder paste;

[0011] Component B includes curing agent, accelerator, and solvent B;

[0012] In component A, based on 100 parts by weight of the epoxy resin:

[0013]

[0014]

[0015] In component B, based on 100 parts by weight of the curing agent: 100 parts by weight of curing agent;

[0016] Accelerator 0.5-5 parts by weight;

[0017] Solvent B: 10-50 parts by weight. In a preferred embodiment of the present invention: Component A comprises, based on 100 parts by weight of the epoxy resin:

[0018] In component B, based on 100 parts by weight of the curing agent: 100 parts by weight of curing agent;

[0019] Accelerator 0.5-2 parts by weight;

[0020] Solvent B: 10-30 parts by weight;

[0021] The weight ratio of component A to component B is 100:(10-50), preferably 100:(12-45).

[0022] In a preferred embodiment of the present invention:

[0023] The double-layer coated hollow glass microspheres are prepared by mixing and reacting raw materials including epoxy resin to be modified, rust-catching filler, isocyanate prepolymer, catalyst and reaction solvent under a protective gas atmosphere.

[0024] In a preferred embodiment of the present invention:

[0025] The weight ratio of the epoxy resin to be modified, the rust-catching filler, and the isocyanate prepolymer is (5-15):(1-5):1, preferably (8-12):(1.5-3.8):1; and / or,

[0026] The catalyst is used in an amount of 0.01 wt% to 5 wt% of the isocyanate prepolymer, preferably 0.1 wt% to 1 wt%; and / or,

[0027] The amount of the reaction solvent is 20-40 wt% of the epoxy resin to be modified, preferably 25-30 wt%; and / or,

[0028] The reaction temperature of the mixture is 80℃~100℃, preferably 80℃~90℃, and / or the reaction time is 1~5 hours, preferably 2~3 hours.

[0029] In a preferred embodiment of the present invention:

[0030] The rust-catching filler is prepared by immersing hollow glass microspheres in a solution comprising tannic acid, a second silane coupling agent, and an immersion solvent, followed by low-temperature freeze-drying; and / or,

[0031] The isocyanate prepolymer is prepared by vacuum dehydration and cooling of dimer polyester polyol, followed by a prepolymerization reaction with isocyanate under a protective gas atmosphere; and / or,

[0032] The epoxy resin to be modified is at least one of bisphenol A type epoxy resins, preferably at least one of bisphenol A epoxy resin 618, bisphenol A epoxy resin 6101, bisphenol A epoxy resin 601, and bisphenol A epoxy resin 604; preferably, the epoxy equivalent of the epoxy resin to be modified is 150 to 1000; and / or,

[0033] The catalyst is at least one selected from sulfuric acid, perchloric acid, sodium methoxide, lithium methoxide, potassium eicosyl sulfonate, alkali metal hydroxide, triarylphosphine, triphenylphosphine, stannous octanoate, dibutyltin dilaurate, and ferric bromide; and / or,

[0034] The reaction solvent is a mixture of xylene and at least one of butyl acetate, propylene glycol methyl ether acetate, and dipropylene glycol dimethyl ether. Preferably, the weight ratio of xylene to at least one of butyl acetate, propylene glycol methyl ether acetate, and dipropylene glycol dimethyl ether is (1.5-1):1.

[0035] In a preferred embodiment of the present invention:

[0036] The weight ratio of the soaking solvent, tannic acid, second silane coupling agent, and hollow glass microspheres is (0.4–2):(0.1–0.5):(0.1–0.5):1, preferably (0.8–1.6)(0.2–0.4):(0.25–0.4):1; and / or,

[0037] The weight ratio of the isocyanate to the dimer polyester polyol is 1:(0.5-10), preferably 1:(0.9-6).

[0038] In a preferred embodiment of the present invention:

[0039] The standard median particle size of the hollow glass microspheres is 18–60 μm, preferably 30–50 μm; and / or,

[0040] The tannic acid mentioned is a commonly used tannic acid in this field, and can be chemically pure or analytically pure; and / or,

[0041] The second silane coupling agent is at least one of vinyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane (such as silane coupling agent KH560, silane coupling agent A187), and γ-aminopropyltriethoxysilane (such as silane coupling agent KH550); and / or,

[0042] The soaking solvent is a mixture of water and ethanol, preferably, the weight ratio of water to ethanol is (0.5-2):1, more preferably (0.6-1.5):1; and / or,

[0043] The isocyanate is at least one selected from 2,6-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, carbodiimide-urea-ketimide modified 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, and polymethyl polyphenyl isocyanate; and / or

[0044] The molecular weight of the dimer acid polyester polyol is 1000 to 10000.

[0045] In a preferred embodiment of the present invention:

[0046] The soaking temperature is 10–50°C, preferably 20–40°C, and / or the soaking time is 1–4 hours, preferably 2–3 hours; and / or,

[0047] The low-temperature freeze-drying temperature is -30℃ to -90℃, preferably -40℃ to -80℃, and / or the time is 1 to 5 hours, preferably 2 to 4 hours; and / or,

[0048] The vacuum dehydration temperature is 110–150°C, and / or the vacuum degree is -0.08 Pa to -0.10 Pa, and / or the time is 0.5 h to 2 h; and / or,

[0049] The temperature after cooling is below 60°C; and / or,

[0050] The reaction temperature of the prepolymerization reaction is 80℃~100℃, preferably 80℃~90℃, and / or the reaction time is 1~4 hours, preferably 2~3 hours.

[0051] In a preferred embodiment of the present invention:

[0052] The epoxy resin is at least one of liquid bisphenol A epoxy resins, preferably at least one of bisphenol A epoxy resin 618, bisphenol A epoxy resin 6101, bisphenol A epoxy resin 601, bisphenol A epoxy resin 604, and bisphenol A epoxy resin 618; and / or,

[0053] The thixotropic agent is at least one of organobentonite, modified hydrogenated castor oil, polyamide wax powder (such as polyamide wax powder ultra, polyamide wax powder 8056, polyamide wax powder OPTIMA), and fumed silica; preferably, the polyamide wax powder is hydrogenated castor oil modified polyamide wax powder (such as castor oil modified polyamide wax powder ST); and / or,

[0054] The wetting and dispersing agent is at least one of the following: polyacrylate solution (e.g., wetting and dispersing agent BYK-S706), block copolymer with basic pigment affinity groups (e.g., wetting and dispersing agent BYK-2155), alkyl ammonium salt type wetting and dispersing agent of high molecular weight copolymer (e.g., wetting and dispersing agent BYK-9076), acrylic dispersant (e.g., wetting and dispersing agent BYK-359), organosilicon surfactant, acid-containing copolymer solution (e.g., wetting and dispersing agent Disponer9250), and alkyl ammonium salt solution of polycarboxylic acid (e.g., wetting and dispersing agent BYK-203); and / or,

[0055] The pigment is at least one selected from carbon black, iron oxide red, iron oxide yellow, titanium dioxide, and phthalocyanine blue; and / or,

[0056] Solvent A is n-butanol and optionally xylene; and / or

[0057] The defoamer is a commonly used defoamer in the art, such as at least one of defoamer BYK-530, defoamer BYK-085, and defoamer BYK-066; and / or,

[0058] The first silane coupling agent is at least one of vinyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane (such as silane coupling agent KH560, silane coupling agent A187), and γ-aminopropyltriethoxysilane (such as silane coupling agent KH550); and / or,

[0059] The aluminum powder slurry is a non-floating aluminum powder slurry (such as non-floating aluminum powder slurry 2501); and / or,

[0060] The curing agent is at least one of phenolic amide curing agents (such as phenolic amide curing agent LITE3040, phenolic amide curing agent LITE3025, and phenolic amide curing agent LITE3060), preferably a cashew nut phenol-modified phenolic amide curing agent; the cashew nut phenol-modified phenolic amide curing agent has a long aliphatic side chain of cashew nut phenol, which has good hydrophobicity, enabling the coating to exhibit excellent water resistance and surface tolerance, while also possessing the advantages of polyamides and phenolic amines, and has a high tolerance to substrate surfaces; and / or,

[0061] The accelerator is an epoxy curing accelerator, preferably at least one of triethylenediamine, 2,4,6-tris(dimethylaminomethyl)phenol (accelerator DMP-30), and benzyldimethylamine, more preferably 2,4,6-tris(dimethylaminomethyl)phenol; and / or,

[0062] The solvent B is n-butanol and optionally xylene, preferably a mixture of n-butanol and xylene, and more preferably, the weight ratio of n-butanol to xylene is (0.3-1.5):1.

[0063] The second objective of this invention is to provide a method for preparing a low-density epoxy primer that strongly adheres to H-grade flash rust surfaces, as described in one objective of this invention.

[0064] The method for preparing a low-density epoxy primer with strong adhesion to H-grade flash rust surfaces, as described in this invention, comprises:

[0065] The A component is prepared by mixing the components according to the specified amount; the B component is prepared by mixing the components according to the specified amount; and the epoxy primer is prepared by mixing the A component and the B component.

[0066] Specifically, the preparation method for component A can adopt the following scheme:

[0067] (1) Preparation of double-layer coated hollow glass microspheres:

[0068] Step 1: Synthesis of rust-catching filler (surface modification of hollow glass microspheres): The surface of hollow glass microspheres is chemically modified using a second silane coupling agent and tannic acid. The hollow glass microspheres are immersed in a solution containing the second silane coupling agent, tannic acid and immersion solvent at 10-50°C for 1-4 hours, and then freeze-dried to remove water and ethanol.

[0069] Step 2: Synthesis of isocyanate prepolymer: Dimeric acid polyester polyol is dehydrated under vacuum at 110-150℃. The dehydrated dimeric acid polyester polyol and isocyanate are added to a reactor under a protective gas atmosphere (nitrogen). The reaction temperature is maintained at 80℃-100℃ for 1-4 hours. The isocyanate content is measured and the product is discharged.

[0070] Step 3: In another reactor, the epoxy resin to be modified is dehydrated under vacuum. The catalyst is added while stirring, and the isocyanate prepolymer synthesized above is gradually added. The temperature is gradually raised to 80-100℃ for reaction. Then the rust-catching filler synthesized above is added, and the reaction solvent is added and stirred evenly. The temperature is raised to 80-100℃ for reaction, the epoxy value is measured, and the temperature is lowered to room temperature before discharge.

[0071] (2) Select a paint mixing tank, add epoxy resin, double-layer coated hollow glass microspheres and thixotropic agent into it, disperse at high speed for 5 to 10 minutes to make the thixotropic agent completely and evenly dispersed, add wetting and dispersing agent at low speed and stir evenly.

[0072] (3) Add 80% of solvent A, pigment, talc powder and barium sulfate in sequence under low speed dispersion, stir at high speed for 30 to 50 minutes to 50 to 70°C, disperse to fineness ≤80μm, add the remaining solvent A, defoamer, first silane coupling agent and aluminum powder slurry and stir evenly, then discharge.

[0073] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0074] I. The double-layer coated hollow glass microspheres used in this invention introduce isocyanate prepolymer and rust-catching filler (modified hollow glass microspheres) into the epoxy resin molecules to be modified, improving the compatibility between the hollow glass microspheres and the epoxy resin to be modified, allowing the rust-catching filler (modified hollow glass microspheres) to be uniformly dispersed in the paint. For example... Figure 1-3As shown, ① in the initial stage of coating, i.e. before curing, when the paint film comes into contact with the low-treatment surface, the tannic acid on the surface of the hollow glass microspheres can adsorb the rust on the substrate surface and react with it; ② during curing, the hollow glass microspheres, utilizing their low specific gravity, gradually detach the adsorbed reactants from the substrate surface and float to the middle or upper layer of the paint liquid; ③ after curing, the rust adsorbed by the hollow glass microspheres can act as a filler in the epoxy resin paint, without affecting the adhesion of the paint film to the substrate, thus ensuring high adhesion. The epoxy primer of this invention not only improves the adhesion of H-grade flash rust surfaces, but also utilizes the low specific gravity of the hollow glass microspheres to achieve the requirement of lightweight coating.

[0075] Second, the isocyanate prepolymer obtained by prepolymerizing isocyanate and dimer polyester polyol in this invention increases the degree of molecular crosslinking and toughness of the system, improves the reactivity, impact resistance, adhesion and peel strength of epoxy resin, and enhances its adhesion to the substrate surface.

[0076] Third, the low-density epoxy primer with strong adhesion to H-grade flash rust surfaces provided by this invention solves the technical problem that existing technologies cannot be used simultaneously for mechanical rust removal, manual rust removal, and water blasting rust removal. After water blasting, the primer exhibits high adhesion and excellent salt spray resistance, especially on H-grade heavily rusted surfaces, regardless of the flash rust level. It is suitable for anti-corrosion coating in shipbuilding, bridges, steel structures, and other fields, and is particularly suitable for direct application to flash rusted surfaces, simplifying surface treatment procedures and improving construction efficiency and economy. Attached Figure Description

[0077] Figure 1 This is a schematic diagram of the curing process of the low-density epoxy primer that strongly adheres to H-grade flash rust surfaces according to the present invention;

[0078] Figure 2 This is a microscopic schematic diagram of the curing process of the low-density epoxy primer with strong adhesion to H-grade flash rust surfaces, as described in this invention, before curing.

[0079] Figure 3 This is a microscopic schematic diagram of the curing process of the low-density epoxy primer that strongly adheres to H-grade flash rust surfaces according to the present invention. Detailed Implementation

[0080] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0081] The raw materials used in the embodiments and comparative examples of this invention are all commercially available raw materials.

[0082] The testing methods used in the embodiments and comparative examples of this invention are as follows:

[0083] Density: Tested according to GB / T 6750;

[0084] Salt spray resistance (5000h): Tested according to GB / T1771;

[0085] Resistance to cathodic disbondment (6 months, distance from the artificial opening in the disbondment area): tested according to GB / T7790 standard;

[0086] Adhesion: Tested according to GB / T 5210 standard.

[0087]

Example 1

[0088] Preparation of component A:

[0089] (1) Preparation of double-layer coated hollow glass microspheres:

[0090] Step 1: Preparation of rust-catching filler (surface modification of hollow glass microspheres): Take 20 parts by weight of tannic acid and 25 parts by weight of silane coupling agent KH560 and add them to a mixed solution of 80 parts by weight of water and ethanol in a weight ratio of 1:1, and stir evenly; add 100 parts by weight of standard hollow glass microspheres with a median particle size of 30 μm and the above mixed liquid to a powder mixer, mix thoroughly, soak at 20℃ for 3 hours, and then freeze-dry to remove water and ethanol to obtain rust-catching filler (modified hollow glass microspheres);

[0091] Step 2: Synthesis of isocyanate prepolymer: Take 288 parts by weight of dimer polyester polyol (functionality 2, molecular weight 1000), dehydrate it under vacuum at 120°C for 2 hours, cool it down to 60°C, add 100 parts by weight of 2,6-toluene diisocyanate while stirring, stir thoroughly, gradually raise the temperature to 80°C, keep it at that temperature for 2 hours, and determine the isocyanate content. The obtained product is the isocyanate prepolymer.

[0092] Step 3: In a separate reaction vessel, take 8 parts by weight of bisphenol A epoxy resin 601, 1 part by weight of xylene, and 1 part by weight of dipropylene glycol dimethyl ether. Heat to 60°C and stir for half an hour until fully dissolved. Then add 1 part by weight of isocyanate prepolymer and stir for 15 minutes until fully mixed. While stirring, add 1 wt% of stannous octoate from the isocyanate prepolymer and gradually raise the temperature to 90°C. Keep at this temperature for 2.5 hours. While stirring, add 1.5 parts by weight of rust-catching filler (modified hollow glass microspheres). Keep at 90°C for 1 hour and determine the epoxy value. The resulting product is double-layer coated hollow glass microspheres.

[0093] (2) Component A is prepared by high-speed dispersion of bisphenol A epoxy resin 618, double-layer coated hollow glass microspheres, barium sulfate, talc, carbon black, titanium dioxide, polyamide wax powder ultra, wetting and dispersing agent BYK-359, defoamer BYK-530, silane coupling agent KH560, xylene, n-butanol, and non-floating aluminum powder slurry 2501 according to the proportions in Table 1.

[0094] Preparation of component B:

[0095] Phenolic amide curing agent LITE3040, accelerator DMP-30, xylene, and n-butanol were added to a paint-making tank according to the proportions in Table 1 below, and the mixture was stirred at high speed for 30 minutes using a high-speed shear dispersion device to obtain component B.

[0096] The weight ratio of component A to component B is 100:14.

[0097] Table 1

[0098] Component A weight Epoxy Resin WSR618 100 Double-layer coated hollow glass microspheres 207.9 Barium sulfate 110 talcum powder 140 Titanium Dioxide 2.7 carbon black 0.31 Non-floating aluminum powder paste 2501 40 Ultra polyamide wax powder 6.8 Silane coupling agent KH560 4.2 wetting and dispersing agent BYK-359 3 Defoamer BYK530 3.96 xylene 84.6 n-Butanol 16.4 Component B Phenolic amide curing agent LITE3040 100 Accelerator DMP-30 2 xylene 5 n-Butanol 5

[0099]

Example 2

[0100] Preparation of component A:

[0101] (1) Preparation of double-layer coated hollow glass microspheres:

[0102] Step 1: Preparation of rust-catching filler (surface modification of hollow glass microspheres): Take 20 parts by weight of tannic acid and 40 parts by weight of silane coupling agent KH560 and add them to a mixed solution of 100 parts by weight of water and ethanol in a weight ratio of 1:1. Stir evenly. Add 100 parts by weight of hollow glass microspheres with a standard median particle size of 50 μm and the above mixed liquid to a powder mixer. Mix evenly and soak at 40℃ for 3 hours. Then freeze dry to remove water and ethanol to obtain rust-catching filler (modified hollow glass microspheres).

[0103] Step 2: Synthesis of isocyanate prepolymer: Take 600 parts by weight of dimer polyester polyol (functionality 2, molecular weight 2000), dehydrate it under vacuum at 120℃ for 2 hours, cool it down to 60℃, add 100 parts by weight of 2,6-toluene diisocyanate while stirring, stir thoroughly, gradually raise the temperature to 80℃, keep it at the temperature for 2 hours, and determine the isocyanate content. The obtained product is the isocyanate prepolymer.

[0104] Step 3: In a separate reactor, take 8 parts by weight of bisphenol A epoxy resin 6101, 1 part by weight of xylene, 1 part by weight of dipropylene glycol dimethyl ether, and 1 part by weight of isocyanate prepolymer. Stir for 15 minutes until fully mixed. While stirring, add 0.1 wt% of dibutyltin dilaurate from the isocyanate prepolymer. Gradually raise the temperature to 90°C and keep it at that temperature for 2.5 hours. While stirring, add 1.5 parts by weight of rust-capturing filler (modified hollow glass microspheres). Keep it at 90°C for 1 hour. Measure the epoxy value. The obtained product is double-layer coated hollow glass microspheres.

[0105] (2) Component A is prepared by high-speed dispersion of bisphenol A epoxy resin 618, double-layer coated hollow glass microspheres, barium sulfate, talc, iron oxide red, polyamide wax powder ultra, wetting and dispersing agent BYK-2155, defoamer BYK-530, silane coupling agent KH560, xylene, n-butanol and non-floating aluminum powder slurry 2501 according to the proportions in Table 2.

[0106] Preparation of component B:

[0107] Phenolic amide curing agent LITE3040, accelerator DMP-30, xylene, and n-butanol were added to a paint-making tank according to the proportions in Table 1 below, and the mixture was stirred at high speed for 30 minutes using a high-speed shear dispersion device to obtain component B. The weight ratio of component A to component B was 100:16.

[0108] Table 2

[0109] Component A weight Epoxy Resin WSR618 100 Double-layer coated hollow glass microspheres 150 Barium sulfate 90 talcum powder 125 Iron oxide red 3 Non-floating aluminum powder paste 2501 43.8 Ultra polyamide wax powder 5 Silane coupling agent KH560 6 wetting and dispersing agent BYK-2155 1.8 Defoamer BYK-530 2 xylene 121.6 n-Butanol 27.4 Component B Phenolic amide curing agent LITE3040 100 Accelerator DMP-30 2 xylene 15 n-Butanol 4.6

[0110]

Example 3

[0111] Preparation of component A:

[0112] (1) Preparation of double-layer coated hollow glass microspheres:

[0113] Step 1: Preparation of rust-catching filler (surface modification of hollow glass microspheres): Take 40 parts by weight of tannic acid and 25 parts by weight of silane coupling agent KH560 and add them to a mixed solution of 160 parts by weight of water and ethanol in a weight ratio of 1:1. Stir evenly. Add 100 parts by weight of standard hollow glass microspheres with a median particle size of 40 μm and the mixed liquid to a powder mixer. Mix thoroughly and soak at 40℃ for 2 hours. Then freeze dry to remove water and ethanol to obtain rust-catching filler (modified hollow glass microspheres).

[0114] Step 2: Synthesis of isocyanate prepolymer: Take 90 parts by weight of dimer polyester polyol (functionality 2, molecular weight 2000) and dehydrate it under vacuum at 120°C for 2 hours. Cool it down to 60°C and add 100 parts by weight of 2,4'-diphenylmethane diisocyanate while stirring. Stir thoroughly and gradually heat it to 80°C and keep it at that temperature for 2 hours. Measure the isocyanate content. The product obtained is the isocyanate prepolymer.

[0115] Step 3: In a separate reaction vessel, take 12 parts by weight of bisphenol A epoxy resin 6101, 1.8 parts by weight of xylene, and 1.2 parts by weight of dipropylene glycol dimethyl ether. Heat to 60°C and stir for half an hour until fully dissolved. Then add 1 part by weight of isocyanate prepolymer and stir thoroughly. While stirring, add 0.1 wt% of dibutyltin dilaurate from the isocyanate prepolymer. Gradually raise the temperature to 90°C and keep it at that temperature for 2.5 hours. While stirring, add 3.8 parts by weight of rust-capturing filler (modified hollow glass microspheres). Keep at 90°C for 1 hour and determine the epoxy value. The resulting product is double-layer coated hollow glass microspheres.

[0116] (2) Component A was prepared by high-speed dispersion of the following components: bisphenol A epoxy resin 6101, double-layer coated hollow glass microspheres, talc powder, barium sulfate, iron oxide red, polyamide wax powder 8056, wetting and dispersing agent BYK-203, defoamer BYK-066, silane coupling agent KH560, xylene, n-butanol, and non-floating aluminum powder paste 2501.

[0117] Preparation of component B:

[0118] Phenolic amide curing agent LITE3025, accelerator DMP-30, xylene, and n-butanol were added to the paint preparation tank according to the proportions in Table 3 below, and the mixture was stirred at high speed for 30 minutes using a high-speed shear dispersion device to obtain component B.

[0119] The weight ratio of component A to component B is 100:19.

[0120] Table 3

[0121] Component A weight Bisphenol A epoxy resin 6101 100 Double-layer coated hollow glass microspheres 250 Barium sulfate 102.3 talcum powder 150 Iron oxide red 3 Non-floating aluminum powder paste 2501 60 Polyamide wax powder 8056 6.7 Silane coupling agent KH560 5.4 wetting and dispersing agent BYK-203 3.7 Defoamer BYK-066 3.1 xylene 73.8 n-Butanol 10.6 Component B Phenolic amide curing agent LITE3025 100 Accelerator DMP-30 0.8 xylene 18 n-Butanol 12

[0122]

Example 4

[0123] Preparation of component A:

[0124] (1) The preparation of double-layer coated hollow glass microspheres is the same as in Example 1;

[0125] (2) Component A is prepared by high-speed dispersion of bisphenol A epoxy resin 6101, double-layer coated hollow glass microspheres, talc powder, barium sulfate, titanium dioxide, carbon black, castor oil modified polyamide wax powder ST, wetting and dispersing agent BYK-203, defoamer BYK-066, silane coupling agent KH560, xylene, n-butanol, and non-floating aluminum powder paste 2501 according to the proportions in Table 4.

[0126] Preparation of component B:

[0127] Phenolic amide curing agent LITE3060, phenolic amide curing agent LITE3040, accelerator DMP-30, xylene, and n-butanol were added to the paint preparation tank according to the proportions in Table 4 below, and the mixture was stirred at high speed for 30 minutes using a high-speed shear dispersion device to obtain component B.

[0128] The weight ratio of component A to component B is 100:12.

[0129] Table 4

[0130] Component A weight Bisphenol A epoxy resin 6101 100 Double-layer coated hollow glass microspheres 189 Barium sulfate 110.4 talcum powder 120 Titanium Dioxide 9.8 carbon black 0.2 Non-floating aluminum powder paste 2501 60 Castor oil modified polyamide wax powder ST 13 Silane coupling agent KH560 3 wetting and dispersing agent BYK-203 2.5 Defoamer BYK-066 2.7 xylene 93.6 n-Butanol 23.9 Component B Phenolic amide curing agent LITE3060 80 Phenolic amide curing agent LITE3040 20 Accelerator DMP-30 0.8 xylene 12.5 n-Butanol 10

[0131]

Example 5

[0132] Preparation of component A:

[0133] (1) The preparation of double-layer coated hollow glass microspheres is the same as in Example 3;

[0134] (2) Component A is prepared by high-speed dispersion of bisphenol A epoxy resin 618, double-layer coated hollow glass microspheres, barium sulfate, talc, iron oxide red, polyamide wax powder OPTIMA, wetting and dispersing agent BYK-9076, defoamer BYK-085, silane coupling agent A187, xylene, n-butanol and non-floating aluminum powder slurry 2501 according to the proportions in Table 5.

[0135] Preparation of component B:

[0136] Phenolic amide curing agent LITE3005, accelerator DMP-30, xylene, and n-butanol were added to the paint preparation tank according to the proportions in Table 5 below, and the mixture was stirred at high speed for 30 minutes using a high-speed shear dispersion device to obtain component B.

[0137] The weight ratio of component A to component B is 100:44.

[0138] Table 5

[0139] Component A weight Bisphenol A epoxy resin 618 100 Double-layer coated hollow glass microspheres 232.6 Barium sulfate 120 talcum powder 130.5 wetting and dispersing agent BYK-9076 1.2 Iron oxide red 5 OPTIMA polyamide wax powder 8.1 Non-floating aluminum powder paste 2501 50.3 Silane coupling agent A187 4.2 Defoamer BYK-085 2.1 xylene 87.4 n-Butanol 12.8 Component B Phenolic amide curing agent LITE3005 100 Accelerator DMP-30 0.5 xylene 9.5 n-Butanol 5.3

[0140] Comparative Example 1

[0141] Comparative Example 1, unlike Example 1, did not use double-layered hollow glass microspheres; instead, it used an equal amount of epoxy resin 601. The specific preparation method is as follows:

[0142] Preparation of component A:

[0143] Component A is prepared by high-speed dispersion of bisphenol A epoxy resin 618, bisphenol A epoxy resin 601, barium sulfate, talc, carbon black, titanium dioxide, polyamide wax powder ultra, wetting and dispersing agent BYK-359, defoamer BYK-530, silane coupling agent KH560, xylene, n-butanol, and non-floating aluminum powder slurry 2501 according to the proportions in Table 6.

[0144] Preparation of component B:

[0145] Phenolic amide LITE3040, accelerator DMP-30, xylene, and butanol were added to a paint-making tank according to the proportions in Table 6 below, and the mixture was stirred at high speed for 30 minutes using a high-speed shear dispersion device to obtain component B.

[0146] The weight ratio of component A to component B is 100:17.3.

[0147] Table 6

[0148] Component A weight Bisphenol A epoxy resin 618 100 Bisphenol A epoxy resin 601 207.9 Barium sulfate 110 talcum powder 140 Titanium Dioxide 2.7 carbon black 0.31 Non-floating aluminum powder paste 2501 40 Ultra polyamide wax powder 6.8 Silane coupling agent KH560 4.2 wetting and dispersing agent BYK-359 3 Defoamer BYK530 3.96 xylene 84.6 n-Butanol 16.4 Component B Phenolic amide curing agent LITE3040 100 Accelerator DMP-30 2 xylene 5 n-Butanol 5

[0149] Sample preparation:

[0150] 1. Substrate preparation:

[0151] Thoroughly remove grease with a suitable cleaning agent, and rinse with (high-pressure) fresh water to remove salt and other contaminants. Sandblast to Sa2.5 (ISO 8501-1:2007), with a surface roughness equivalent to Rugotest No. 3 N9a to N10, Keane-Tator Comparison Plate 2.0 (sandblasting / shot peening), or ISO Comparison Plate Fine-Medium Roughness (sandblasting); or blast with water to Wa2-Wa2.5 (atmospheric exposure) / minimum Wa2.5 (immersion) (ISO 8501-1:2007). Before application, classify flash rust according to standard ISO 8501-4:2006.

[0152] The visible appearance of flash rust on the steel surface after water spraying. Refer to standard GB / T8923.4-2013 (same as ISO8501-4:2006). Based on the degree of flash rust, it is divided into three grades: L, M, and H.

[0153] 2. Preparation of the paint film:

[0154] Examples 1-5 and Comparative Example 1 were mixed and stirred thoroughly according to the weight ratio of components A and B. The density of the coating was tested in a constant temperature and humidity spray booth, and the paint film was sprayed using a high-pressure airless sprayer. The preparation requirements of the paint film (including thickness, etc.) were prepared in accordance with the relevant test standards, and the relevant properties of the paint film were tested.

[0155] (1) Density test data are shown in Table 7 below:

[0156] Table 7

[0157]

[0158] (2) Salt spray resistance (5000h) test data are shown in Table 8 below:

[0159] Table 8

[0160]

[0161] (3) The test data for resistance to cathode stripping (6 months) are shown in Table 9 below:

[0162] Table 9

[0163]

[0164] (4) The adhesion test data are shown in Table 10 below:

[0165] Table 10

[0166]

[0167] The test data from Examples 1-5 and Comparative Example 1 show that the introduction of double-layered hollow glass microspheres significantly reduces the density of the coating. The density of the epoxy primer prepared by this invention is 84.5% to 86.5% of that in Comparative Example 1. The introduction of isocyanate and dimer acid-structured isocyanate prepolymers and modified glass microspheres into the epoxy resin molecules of the double-layered hollow glass microspheres in this invention improves the coating's resistance to various media, especially on water-blasted M-grade and H-grade steel structures, significantly enhancing salt spray resistance and cathodic disbondment performance. After more than 5000 hours of salt spray resistance, the coating film shows no blistering, peeling, or corrosion. After 6 months of cathodic disbondment, the distance at the artificial opening in the disbondment area is significantly reduced, from 19 mm in Comparative Example 1 to less than 8 mm. Adhesion is significantly improved, from 3.5 MPa in Comparative Example 1 to over 6 MPa.

[0168] The epoxy primer prepared in Example 155 of this invention has a low density, effectively achieving lightweight coating. It has excellent adhesion, salt spray resistance, and cathodic disbondment resistance on surfaces treated by manual rust removal, mechanical rust removal, and water blasting. It has a high tolerance for flash rust on water blasting treated surfaces and can be adapted to H-grade flash rust surfaces.

Claims

1. A low density epoxy primer for high adhesion to H-class flash rusted surfaces, characterized in that The epoxy primer comprises raw materials of the following components: A component and a B component; The A component comprises an epoxy resin, double-coated hollow glass microspheres, a thixotropic agent, a wetting dispersant, a pigment, barium sulfate, talc, a solvent A, a defoaming agent, a first silane coupling agent, and an aluminum paste; The B component comprises a curing agent, an accelerator, and a solvent B; In the A component, based on 100 parts by weight of the epoxy resin: 100 parts by weight of the epoxy resin; 100-300 parts by weight of the double-coated hollow glass microspheres; 5-15 parts by weight of the thixotropic agent; 0.5-5 parts by weight of the wetting dispersant; 1-10 parts by weight of the pigment; 60-200 parts by weight of the barium sulfate; 60-200 parts by weight of the talc; 60-150 parts by weight of the solvent A; 1-5 parts by weight of the defoaming agent; 1-10 parts by weight of the first silane coupling agent; 40-100 parts by weight of the aluminum paste; In the B component, based on 100 parts by weight of the curing agent: 100 parts by weight of the curing agent; 0.5-5 parts by weight of the accelerator; 10-50 parts by weight of the solvent B; The double-coated hollow glass microspheres are prepared by mixing raw materials including a to-be-modified epoxy resin, a rust-trapping filler, an isocyanate prepolymer, a catalyst, and a reaction solvent under a protective gas atmosphere, and comprise: Step 1: Synthesis of the rust-trapping filler: the surface of hollow glass microspheres is chemically modified using a second silane coupling agent and tannic acid, the hollow glass microspheres are soaked in a solution including the second silane coupling agent, the tannic acid, and a soaking solvent, and are soaked at 10-50℃ for 1-4 hours, and water and ethanol are removed by freeze-drying at low temperature; Step 2: Synthesis of the isocyanate prepolymer: dimer acid polyester polyol is vacuum-dried at 110-150℃, the dimer acid polyester polyol after water removal and isocyanate are added to a reaction kettle under a protective gas atmosphere, the reaction temperature is kept at 80-100℃ for 1-4 hours, the isocyanate content is measured, and the product is discharged; Step 3: Another reaction kettle is used, the to-be-modified epoxy resin is vacuum-dried, the catalyst is added under stirring, the above-synthesized isocyanate prepolymer is gradually added, the temperature is gradually increased to 80-100℃ for reaction, then the above-synthesized rust-trapping filler is added, the reaction solvent is added and stirred uniformly, the temperature is increased to 80-100℃ for reaction, the epoxy value is measured, the temperature is decreased to room temperature, and the product is discharged.

2. The epoxy primer according to claim 1, wherein, in the A component, based on 100 parts by weight of the epoxy resin: 100 parts by weight of the epoxy resin; 150-250 parts by weight of the double-coated hollow glass microspheres; 5-13 parts by weight of the thixotropic agent; 1.8-3 parts by weight of the wetting dispersant; 3-10 parts by weight of the pigment; 90-120 parts by weight of the barium sulfate; 120-150 parts by weight of the talc; 100-150 parts by weight of the solvent A; 2-4 parts by weight of the defoaming agent; 3-6 parts by weight of the first silane coupling agent; 40-80 parts by weight of the aluminum paste; In the B component, based on 100 parts by weight of the curing agent: 100 parts by weight of the curing agent; 0.5-2 parts by weight of the accelerator; 10-30 parts by weight of the solvent B; The weight ratio of the A component to the B component is 100:(10-50). ​ 3.The epoxy primer according to claim 2, characterized in that: the weight ratio of the A component and the B component is 100: (12-45). 4.The epoxy primer according to claim 1, characterized in that: the weight ratio of the epoxy resin to be modified, the rust capturing filler and the isocyanate prepolymer is (5-15) : (1-5) : 1; and / or, the amount of the catalyst is 0.01wt%-5wt% of the isocyanate prepolymer; and / or, the amount of the reaction solvent is 20-40wt% of the epoxy resin to be modified; and / or, the reaction temperature of the mixed reaction is 80℃-100℃, and / or, the reaction time is 1-5 hours. 5.The epoxy primer according to claim 4, characterized in that: the weight ratio of the epoxy resin to be modified, the rust capturing filler and the isocyanate prepolymer is (8-12) : (1.5-3.8) : 1; and / or, the amount of the catalyst is 0.1wt%-1wt% of the isocyanate prepolymer; and / or, the amount of the reaction solvent is 25-30wt% of the epoxy resin to be modified; and / or, the reaction temperature of the mixed reaction is 80℃-90℃, and / or, the reaction time is 2-3 hours. 6.The epoxy primer according to claim 1, characterized in that: the epoxy resin to be modified is at least one of bisphenol A type epoxy resins; and / or, the catalyst is at least one of sulfuric acid, perchloric acid, sodium methoxide, lithium methoxide, potassium eicosyl sulfonate, alkali metal hydroxide, triaryl phosphine hydride, triphenyl phosphine, stannous octoate, dibutyltin dilaurate, ferric bromide; and / or, the reaction solvent is a mixture of at least one of xylene and butyl acetate, propylene glycol methyl ether acetate, dipropylene glycol dimethyl ether. 7.The epoxy primer according to claim 6, characterized in that: the epoxy equivalent weight of the epoxy resin to be modified is 150-1000; and / or, the mixed weight ratio of at least one of xylene and butyl acetate, propylene glycol methyl ether acetate, dipropylene glycol dimethyl ether is (1.5-1) :

1. 8.The epoxy primer according to claim 1, characterized in that: the weight ratio of the tannic acid, the second silane coupling agent and the hollow glass microsphere is (0.1-0.5) : (0.1-0.5) : 1; and / or, the weight ratio of the soaking solvent, the tannic acid, the second silane coupling agent and the hollow glass microsphere is (0.4-2) : (0.1-0.5) : (0.1-0.5) : 1; and / or, the weight ratio of the isocyanate and the dimer acid polyester polyol is 1: (0.5-10). 9.The epoxy primer according to claim 8, characterized in that: the weight ratio of the tannic acid, the second silane coupling agent and the hollow glass microsphere is (0.2-0.4) : (0.25-0.4) : 1; and / or, the weight ratio of the soaking solvent, the tannic acid, the second silane coupling agent and the hollow glass microsphere is (0.8-1.6) (0.2-0.4) : (0.25-0.4) : 1; and / or, The weight ratio of the isocyanate and the dimer acid polyester polyol is 1:(0.9-6).

10. The epoxy primer according to claim 1, wherein: The standard median particle size of the hollow glass microsphere is 18-60 μm; and / or, The second silane coupling agent is at least one of vinyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-aminopropyltriethoxysilane; and / or, The soaking solvent is a mixture of water and ethanol; and / or, The isocyanate is at least one of 2,6-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, carbodiimide-uretonimine-modified 4,4'-diphenylmethane diisocyanate, and 2,4'-diphenylmethane diisocyanate; and / or, The molecular weight of the dimer acid polyester polyol is 1000-10000.

11. The epoxy primer according to claim 10, wherein: The standard median particle size of the hollow glass microsphere is 30-50 μm; and / or, The weight ratio of water to ethanol in the soaking solvent is (0.5-2):

1.

12. The epoxy primer according to claim 11, wherein: The weight ratio of water to ethanol in the soaking solvent is (0.6-1.5):

1.

13. The epoxy primer according to claim 1, wherein: The temperature of the low-temperature freeze-drying is -30°C to -90°C, and / or the time is 1-5 hours; and / or, The temperature of the vacuum dehydration in step 2 is 110-150°C, and / or the vacuum degree is -0.08 Pa to -0.10 Pa, and / or the time is 0.5 h to 2 h.

14. The epoxy primer according to claim 13, wherein: The soaking temperature is 20-40°C, and / or the soaking time is 2-3 hours; and / or, The temperature of the low-temperature freeze-drying is -40°C to -80°C, and / or the time is 2-4 hours; and / or, The reaction temperature of the prepolymerization in step 2 is 80°C to 90°C, and / or the reaction time is 2-3 hours.

15. The epoxy primer according to claim 1 or 2, wherein: The epoxy resin is at least one of a liquid bisphenol A epoxy resin; and / or, The thixotropic agent is at least one of organic bentonite, modified hydrogenated castor oil, polyamide wax powder, and fumed silica; and / or, The wet dispersant is at least one of a polyacrylate solution, a block copolymer containing a basic pigment-affinity group, an alkylammonium salt type wet dispersant of a high-molecular-weight copolymer, an acrylic dispersant, a silicone surfactant, a solution of an acid-group-containing copolymer, and a solution of an alkylammonium salt of a polycarboxylic acid; and / or, The pigment is at least one of carbon black, red iron oxide, yellow iron oxide, titanium white, and phthalocyanine blue; and / or, The solvent A is n-butanol and optionally xylene; and / or, The first silane coupling agent is at least one of vinyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-aminopropyltriethoxysilane; and / or, The aluminum paste is a non-floating type aluminum paste; and / or, The curing agent is at least one of a phenolic amide curing agent; and / or, The accelerator is an epoxy curing accelerator; and / or, The solvent B is n-butanol and optionally dimethylbenzene.

16. The epoxy primer according to claim 15, wherein: The solvent A is a mixture of n-butanol and dimethylbenzene; and / or, The curing agent is a cardanol-modified phenolic amide curing agent; and / or, The accelerator is at least one of triethylenediamine, 2,4,6-tris(dimethylaminomethyl)phenol, and benzyldimethylamine; and / or, The solvent B is a mixture of n-butanol and dimethylbenzene.

17. The epoxy primer according to claim 16, wherein: The weight ratio of n-butanol to dimethylbenzene in the solvent A is (0.1-1):1; and / or, The weight ratio of n-butanol to dimethylbenzene in the solvent B is (0.3-1.5):

1.

18. A process for the preparation of a low density epoxy primer for strong adhesion to H-class flash rusted surfaces according to any one of claims 1 to 17, characterized in that The method comprises: The A component is prepared by mixing the A component in the amount; the B component is prepared by mixing the B component in the amount; and the epoxy primer is prepared by mixing the A component and the B component. The method comprises: The A component is prepared by mixing the A component in the amount; the B component is prepared by mixing the B component in the amount; and the epoxy primer is prepared by mixing the A component and the B component.

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