Modified epoxy resin, two-component epoxy zinc-rich anticorrosive primer and preparation method thereof

Abstract

The present application relates to a kind of anticorrosive coatings, and specifically relates to a kind of two-component epoxy zinc-rich anticorrosive primer and preparation method thereof.For the "deficiency of existing solvent type zinc-rich primer for facilitating spraying construction usually contains more organic solvent, VOC content is higher", the present application uses self-made high solid content modified epoxy resin as base material, while adding graphite powder, carbon fiber, graphene, thereby obtaining a kind of zinc content reduction, low VOC content two-component epoxy zinc-rich anticorrosive primer.The zinc-rich primer provided by the present application has a solid content of more than 95%, significantly reduces the VOC content of the coating, has strong adhesion, good flexibility, excellent salt spray performance, and greatly reduces the cost.

Description

Technical Field

[0001] This invention relates to an anti-corrosion coating, and more specifically, to a two-component epoxy zinc-rich anti-corrosion primer and its preparation method. Background Technology

[0002] Zinc-rich coatings rely on the electrochemical protective effect of zinc powder to protect steel substrates from corrosion, exhibiting excellent anti-corrosion performance. They are widely used in shipbuilding, container manufacturing, marine engineering, petrochemical storage tanks, steel structures, and bridge corrosion protection. Zinc-rich primers are mainly divided into two categories based on their base materials: epoxy zinc-rich primers and inorganic zinc-rich primers. The former uses epoxy resin as a base material, while the latter uses silicate ester prepolymers or inorganic silicates as base materials. Epoxy zinc-rich primers are widely used in marine engineering, shipbuilding and container manufacturing, petrochemical industry storage tanks, pipelines and steel structures, and bridge corrosion protection. The advantages of epoxy zinc-rich primers include good penetration, strong adhesion, and lower requirements for substrate preparation.

[0003] Epoxy zinc-rich primers are mainly divided into two types: water-soluble epoxy zinc-rich primers and solvent-based epoxy zinc-rich primers. Water-soluble epoxy zinc-rich primers are VOC-free and have excellent solvent resistance; however, they have poor flexibility and require high-quality rust removal from the substrate. They are not suitable for use as pre-coating primers or zinc-rich primers in applications requiring high flexibility, such as container manufacturing and railway vehicle manufacturing. Furthermore, because the application of water-soluble epoxy zinc-rich primers is greatly affected by ambient temperature and humidity, solvent-based epoxy zinc-rich primers are still used in most cases. Solvent-based epoxy zinc-rich primers contain a large amount of organic solvents, and their use is becoming increasingly restricted due to growing environmental concerns in China. Currently, the VOC content of coatings is typically reduced by using high-solids or solvent-free epoxy resins and curing agents.

[0004] Chinese patent CN116396661A discloses a salt spray resistant two-component epoxy zinc-rich primer and its preparation method. Component A has the following formulation: 7-10 parts liquid epoxy resin, 10-15 parts solid epoxy resin, 0.1-0.3 parts dispersant, 1-3 parts anti-settling agent, 0.5-1 part thickener, 10-14 parts resin diluent, 65-75 parts anti-rust pigment, and 3-5 parts organic solvent. Component B has the following formulation: 40-50 parts curing agent, 40-50 parts curing diluent, and 0.5-3 parts silane coupling agent. The anti-rust pigment includes nano-inorganic phosphate, polypyrrole nanosheets, zinc powder, ferrophosphorus micropowder, aluminum tripolyphosphate, and modified zinc phosphate. The addition of nano-inorganic phosphate and polypyrrole nanosheets to this salt spray resistant two-component epoxy zinc-rich primer has a synergistic effect in the coating, enhancing its mechanical properties and corrosion resistance.

[0005] Chinese patent CN115353794A discloses a high-solids epoxy zinc-rich primer, wherein the weight ratio of component A to component B is 8-12:1. Component A comprises the following components by weight: 7-9 parts liquid epoxy resin; 0.3-0.6 parts dispersant; 0.4-0.8 parts thixotropic agent; 85-95 parts zinc powder; and 3-4 parts mixed solvent. Component B comprises the following components by weight: 3-4 parts N,N'-dimethylhexanediamine; 4-5 parts modified polyamide curing agent; 4-5 parts pigments and fillers; 0.2-0.4 parts thixotropic agent; 0.1-0.2 parts curing accelerator; and 1-2 parts mixed solvent. Due to the strong electron-donating effect of the methyl groups at both ends of the N,N'-dimethylhexanediamine structure, the secondary amines at both ends of N,N'-dimethylhexanediamine are strongly basic, thus they can react rapidly with the epoxy groups in the epoxy resin, enabling the coating to dry and cure quickly.

[0006] Chinese patent CN112251112A discloses an epoxy zinc-rich primer and its preparation method, wherein the volume ratio of component A to component B is 4:1. Component A: 12-16% epoxy resin, 0.3-0.5% dispersant, 3-6% barium petroleum sulfonate, 50-60% zinc powder, 15-20% composite iron-titanium powder, 5-15% sericite, 0.8-1% organobentonite, 20% mixed solvent, 0.5-1% curing agent, and 0.5-1% defoamer; Component B: 1-2% epoxy accelerator, 75% mixed solvent, 20-28% polyamide resin, and 12-16% xylene. This invention has the advantages of fast drying speed, good adhesion, excellent chemical resistance, good salt spray resistance and water resistance, and the preparation method is simple to operate and highly efficient.

[0007] Existing solvent-based zinc-rich primers often contain a significant amount of organic solvents, resulting in high VOC content. Adding conductive agents such as carbon nanotubes and graphene can improve zinc powder utilization and reduce zinc powder usage, but these conductive agents are expensive, increasing the cost of zinc-rich primers. Summary of the Invention

[0008] To address the shortcomings of existing solvent-based zinc-rich primers, which typically contain a large amount of organic solvents and have high VOC content for easy spraying, this invention modifies the main film-forming substance, epoxy resin, and the epoxy curing agent to obtain a two-component epoxy zinc-rich anti-corrosion primer with low VOC content.

[0009] The zinc powder content of zinc-rich primers typically reaches 60-80% of the dry film weight. During welding, zinc powder volatilization generates zinc mist, which poses a significant health hazard to workers in the workshop. Conversely, reducing the zinc powder content leads to a rapid decline in its anti-corrosion performance. Graphene, as a two-dimensional structural material with an extremely high aspect ratio, can achieve a strong sealing effect with a relatively small dosage, thereby improving the coating's anti-corrosion performance. Therefore, to address the issue of high zinc powder content in zinc-rich primers, this invention adds graphene to a low-VOC two-component epoxy zinc-rich anti-corrosion primer.

[0010] However, graphene has a very large specific surface area, making it difficult to wet and disperse in primers. Without good dispersion of graphene in the primer, its effectiveness in both conductivity and shielding is limited. Furthermore, using graphene alone to improve conductivity significantly increases costs due to its high price. Therefore, this invention adds graphite powder, carbon fiber powder, and a dispersant along with graphene; thus solving the problems of high cost, poor dispersibility, and poor conductivity and shielding effects associated with adding graphene alone.

[0011] This invention uses a self-made silane-acrylic acid copolymer modified epoxy resin as the base material, and zinc powder, graphite powder, carbon fiber powder, multilayer graphene, dispersant, pigments and fillers are combined to prepare zinc powder slurry. A curing agent is prepared by reacting liquid epoxy resin with alicyclic diamine and polyetheramine. Finally, a high-solids long-lasting epoxy zinc-rich anti-corrosion coating with relatively low cost, low VOC content, low zinc powder content, strong adhesion, good flexibility and excellent salt spray performance is obtained.

[0012] One objective of this invention is to provide a modified epoxy resin for a two-component epoxy zinc-rich anti-corrosion primer with low VOC content. This modified epoxy resin can reduce VOC content while ensuring the film performance and spraying performance of the primer; the zinc-rich primer obtained by using this modified epoxy resin as the main film-forming substance has a solid content greater than 95% and a significantly reduced VOC content.

[0013] The modified epoxy resin is prepared by stirring a raw material containing the following components at 50-60°C for 0.5-1 h; the components and their weight parts are as follows:

[0014] 100 parts by weight of liquid epoxy resin;

[0015] 10-30 parts by weight of silane-acrylic acid copolymer, preferably 15-25 parts by weight;

[0016] 5-20 parts by weight of non-reactive diluent, preferably 8-15 parts by weight;

[0017] 5-20 parts by weight of reactive diluent, preferably 8-15 parts by weight.

[0018] The liquid epoxy resin is preferably a bisphenol A type liquid epoxy resin; for example, E-51 or E-44 epoxy resin.

[0019] The inactive diluent is an organic compound with a boiling point above 250°C; preferably selected from one or more of the following: tripropylene glycol butyl ether, diethyl phthalate, dibutyl phthalate, dioctyl terephthalate, acetyl tributyl citrate, dodecyl alcohol ester, and hexadecyl alcohol ester (2,2,4-trimethyl-1,3-pentanediol diisobutyrate).

[0020] The active diluent is preferably selected from one or more of ethylene glycol diglycidyl ether, cashew phenol glycidyl ether, and C12-14 alkyl glycidyl ether.

[0021] The silane-acrylic acid copolymer is a self-made product of this invention; it is copolymerized from a silane prepolymer (prepolymerized by condensation of a silane coupling agent containing double bonds and other silicate monomers) and an acrylic acid monomer. Specifically, the silane-acrylic acid copolymer is prepared from raw materials containing the following components; the components and their weight parts are as follows:

[0022] 100 parts by weight of unsaturated monomer;

[0023] 10-25 parts by weight of silane prepolymer, preferably 12-20 parts by weight;

[0024] The initiator is 1-3 parts by weight, preferably 1.5-2.5 parts by weight;

[0025] Propylene glycol methyl ether 2.5-10 parts by weight, preferably 4-8 parts by weight;

[0026] 2.5-10 parts by weight of tripropylene glycol butyl ether, preferably 4-8 parts by weight;

[0027] The silane-acrylic acid copolymer can be prepared using existing methods. This invention provides a method for preparing the silane-acrylic acid copolymer; the method includes: heating propylene glycol methyl ether and tripropylene glycol butyl ether to boiling; adding 1 / 5-2 / 5 of the unsaturated monomer and 1 / 4 of the initiator, and maintaining the temperature for 15-30 minutes; dropwise adding a mixture consisting of silane prepolymer, the remaining unsaturated monomer, and the initiator, completing the addition over 1.5-2 hours; and continuing to maintain the temperature for 1-1.5 hours after the addition is complete to obtain the silane-acrylic acid copolymer.

[0028] The difference between the self-made silane-acrylic acid copolymer of this invention and existing silane-acrylic acid copolymers is that existing silane-acrylic acid copolymers are copolymerized with acrylic monomers using silane coupling agents containing double bonds. The self-made silane-acrylic acid copolymer of this invention is formed by first condensing a silane coupling agent containing double bonds with silicate ester monomers to form a silane prepolymer, which is then copolymerized with unsaturated monomers (including acrylic monomers). The self-made silane-acrylic acid copolymer of this invention has stronger hydrophobicity and higher hydrolytic stability than silane coupling agents, resulting in coatings with higher salt spray resistance.

[0029] The unsaturated monomer is preferably selected from one or more of styrene, methyl methacrylate, methyl acrylate, glycidyl acrylate, butyl acrylate, and octyl acrylate.

[0030] The initiator is preferably selected from one or more of benzoyl peroxide, tert-butyl peroxide, and dicumyl peroxide.

[0031] The silane prepolymer is a self-made product of this invention. The silane prepolymer is formed by the condensation of a silane coupling agent containing double bonds with a silicate ester monomer. Specifically, the silane prepolymer is prepared from raw materials containing the following components; the components and their weight parts are as follows:

[0032] 100 parts by weight of silane coupling agent;

[0033] 50-150 parts by weight of silicate, preferably 80-120 parts by weight;

[0034] 20-40 parts by weight of propylene glycol methyl ether, preferably 25-35 parts by weight;

[0035] 4-10 parts by weight of ion exchange resin, preferably 5-8 parts by weight;

[0036] 8-20 parts by weight of deionized water, preferably 10-15 parts by weight.

[0037] The method for preparing the silane prepolymer is unique to this invention. The method for preparing the silane prepolymer includes:

[0038] The silicate ester, silane coupling agent, propylene glycol methyl ether, and ion exchange resin are stirred at low speed at 60-65°C for 5-10 minutes; deionized water is added dropwise while stirring continues, and the addition is completed within 1-1.5 hours; after the addition is completed, stirring is continued for 1-1.5 hours; and the mixture is allowed to stand for more than 12 hours to obtain the silane prepolymer; the low speed refers to 50-100 rpm.

[0039] The difference between the self-made silane prepolymer of this invention and existing silane prepolymers is that existing silane prepolymers are generally self-polymerized by condensation of silane coupling agents or self-polymerized by condensation of silicate monomers, while the silane prepolymer of this invention is a copolymerized silane coupling agent and silicate monomers by condensation, which can give full play to the adhesion promoting function of silane coupling agent and the hydrophobic properties of silicate.

[0040] The difference between the preparation method of the silane prepolymer of the present invention and the existing preparation method of silane prepolymer is that the existing method uses hydrochloric acid as a condensation catalyst, while the present invention uses a strong acid ion exchange resin as a catalyst. The advantage is that there is no chloride ion residue and the coating has better anti-corrosion performance.

[0041] The silane coupling agent is selected from one or more of glycidoxypropyltrimethoxysiloxane (560 coupling agent), glycidoxypropyltriethoxysiloxane, methacryloyloxypropyltrimethoxysiloxane (570 coupling agent), methacryloyloxypropyltriethoxysiloxane, vinyltriethoxysilane (A-151), vinyltrimethoxysilane (A-171), and vinyltris(β-methoxyethoxy)silane (A-172 coupling agent).

[0042] The silicate ester is selected from one or more of tetraethyl silicate, dimethyl methyl phenyl silicate, and diethyl diphenyl silicate.

[0043] The ion exchange resin is a strong acid ion exchange resin. For example, Dow's IR100NA, Purolite's C100E, and Shanghai Kaiping Resin's D001*7 resin.

[0044] The deionized water has a conductivity of ≤20μs / cm.

[0045] The second objective of this invention is to provide a two-component epoxy zinc-rich anti-corrosion primer.

[0046] The two-component epoxy zinc-rich anti-corrosion primer is composed of component A and component B in a weight ratio of 7-10:1, preferably 9-10:1.

[0047] Component A includes:

[0048] 100 parts by weight of the modified epoxy resin as described in one of the objectives of the invention;

[0049] Graphene 1-8 parts by weight, preferably 1-6 parts by weight; more preferably 2-5 parts by weight;

[0050] 3-30 parts by weight of carbon fiber powder, preferably 15-25 parts by weight; more preferably 15-25 parts by weight.

[0051] Graphite powder: 10-90 parts by weight, preferably 30-90 parts by weight; more preferably 40-75 parts by weight;

[0052] Dispersant 3-10 parts by weight;

[0053] 200-500 parts by weight of zinc powder, preferably 200-400 parts by weight, more preferably 225-350 parts by weight;

[0054] 50-200 parts by weight of mica iron oxide, preferably 60-150 parts by weight;

[0055] Modified barium sulfate, 20-200 parts by weight, preferably 30-100 parts by weight;

[0056] 20-60 parts by weight of aluminum tripolyphosphate, preferably 25-50 parts by weight;

[0057] Rust-preventive pigment: 50-200 parts by weight, preferably 80-150 parts by weight;

[0058] 5-15 parts by weight of organic bentonite, preferably 8-12 parts by weight;

[0059] 2-8 parts by weight of fumed silica; preferably 3-5 parts by weight;

[0060] Component B is an epoxy curing agent.

[0061] Compared with existing two-component epoxy zinc-rich anti-corrosion primers, the A component of the two-component epoxy zinc-rich anti-corrosion primer of the present invention uses a self-made high-solids-content modified epoxy resin as the base material, and the resulting zinc-rich primer has a solids content of more than 95%, which significantly reduces the VOC content of the coating.

[0062] This invention reduces the amount of zinc powder used by adding graphite powder, carbon fiber powder, and graphene, reducing the zinc powder content by half compared to conventional zinc-rich primers. By rationally combining graphite powder, carbon fiber powder, and graphene, the cost of zinc-rich primers using graphene alone is greatly reduced. Furthermore, it solves the problem that "graphene has a very large specific surface area, making it difficult to wet and disperse in primers, resulting in poor conductivity and shielding effects."

[0063] The graphene is preferably reduced multilayer graphene. Compared to reduced single-layer graphene, the use of reduced multilayer graphene in this invention can significantly reduce costs.

[0064] The graphene preferably has a carbon content of ≥99%; the graphene preferably has a particle size of 1-20 μm, more preferably 2-10 μm; and the graphene preferably has a thickness of 3-30 nm, more preferably 5-15 nm.

[0065] The carbon fiber powder preferably has a mesh size of 200-1500 mesh, more preferably 400-800 mesh; the fiber diameter of the carbon fiber powder is preferably 5-10 μm.

[0066] The graphite powder is preferably flake graphite powder; the mesh size of the graphite powder is preferably 200-3000 mesh, more preferably 400-1200 mesh.

[0067] The dispersant can be any existing dispersant that can be used in zinc-rich primers; the dispersant can be selected from BYK's 104S, 2155, and 9076 dispersants, Hemings' D-983, FN211, and W19 dispersants, EFKA's 4560, and OMG's 0451.

[0068] The zinc powder can be any existing zinc powder that can be used in zinc-rich primers; preferably, it is 500-800 mesh zinc powder.

[0069] The mica iron oxide can be any existing mica iron oxide that can be used in zinc-rich primers; preferably, it is selected from at least one of iron oxide red or mica iron oxide gray.

[0070] The modified barium sulfate refers to silane-modified barium sulfate, and any existing silane-modified barium sulfate that can be used in zinc-rich primers can be selected; for example, ZJ-051, ZJ-101, and ZJ-201 modified barium sulfate from Jiangsu Qunxin Powder Materials.

[0071] The aluminum tripolyphosphate mentioned refers to silica-modified aluminum tripolyphosphate, and any existing silica-modified aluminum tripolyphosphate that can be used in zinc-rich primers can be selected; for example, AZP-99 and AZP-Ⅰ from Guangxi Xinjing Technology.

[0072] The composite zinc silicate is a surface-coated zinc silicate, and any existing zinc silicate that can be used for surface coating of zinc-rich primers can be selected; for example, MP 1085 anti-rust pigment from Shanghai Meijing Chemical New Materials.

[0073] The organic bentonite can be any existing organic bentonite that can be used in zinc-rich primers; for example, it can be BENTONE SD-2, BENGEL 818, 828, 858 from Hemings, or TY-108, TY138, TY158 from Zhejiang Tianyu.

[0074] The fumed silica can be untreated or hydrophobically treated fumed silica, and any existing untreated or hydrophobically treated fumed silica that can be used in zinc-rich primers can be selected; for example, Evonik's A-200 and A-380.

[0075] The anti-rust pigment can be any existing anti-rust pigment suitable for zinc-rich primers; it can be selected from one or more of composite zinc silicate, ferrophosphorus powder, iron-titanium powder, and modified zinc phosphate. Compared with iron-titanium powder and zinc phosphate, composite zinc silicate is less expensive while achieving the same anti-corrosion performance; compared with ferrophosphorus powder, composite zinc silicate has better salt spray resistance. Therefore, the anti-rust pigment is preferably composite zinc silicate.

[0076] The epoxy curing agent is prepared from raw materials containing the following components; the components and their weight parts are as follows:

[0077] 100 parts by weight of epoxy resin;

[0078] 20-40 parts by weight of propylene glycol methyl ether, preferably 22-31 parts by weight;

[0079] 30-50 parts by weight of propylene glycol ethyl ether, preferably 35-45 parts by weight;

[0080] 20-80 parts by weight of isophorone diamine, preferably 30-70 parts by weight;

[0081] 20-100 parts by weight of polyetheramine, preferably 30-80 parts by weight.

[0082] The epoxy resin is preferably a bisphenol A type liquid epoxy resin; for example, E51 or E44 epoxy resin.

[0083] The polyetheramine is preferably a low molecular weight amino-terminated polyether, where low molecular weight means a molecular weight of 200-600; for example, D230, D403, ED-600.

[0084] The preparation method of the epoxy curing agent includes: dissolving epoxy resin in propylene glycol methyl ether and propylene glycol ethyl ether to obtain epoxy resin liquid; heating isophorone diamine and polyetheramine in a nitrogen atmosphere to 50-70°C, adding epoxy resin liquid and continuing to stir and react at 65-70°C for 1-1.5h to obtain the epoxy curing agent; the epoxy resin liquid is added completely in 1-1.5h.

[0085] A two-component epoxy zinc-rich anti-corrosion primer, the formulation of component A is shown in Table 1, and the formulation of component B is shown in Table 2. The ratio of component A to component B is 9-10:1 (by weight).

[0086] Table 1

[0087] Raw material name weight graphene 1-6 carbon fiber powder 10-30 Graphite powder 30-90 dispersant 3-10 Modified epoxy resin 100 Zinc powder 200-400 Mica iron oxide 50-150 Modified barium sulfate 20-100 Aluminum tripolyphosphate 20-50 Composite zinc silicate 50-200 Organic bentonite 8-15 Fumed silica 3-5

[0088] Preparation process of component A:

[0089] Add modified epoxy resin and dispersant to a mixing container and stir at low speed for 5 minutes; add graphite, carbon fiber powder, graphene, and fumed silica and disperse at high speed for 30 minutes; add zinc powder, mica iron oxide, modified barium sulfate, aluminum tripolyphosphate, and composite zinc silicate and stir at high speed for 30 minutes; add organic bentonite and stir at high speed for 30 minutes; filter through a 100-mesh stainless steel screen to obtain component A;

[0090] Table 2

[0091] Raw material name weight Propylene glycol methyl ether 22-31 Propylene glycol ethyl ether 30-50 Epoxy resin 100 Isophorone diamine 20-80 polyetheramine 20-100

[0092] Preparation process of component B: Add epoxy resin, propylene glycol methyl ether and propylene glycol ethyl ether to a flask, stir and dissolve to obtain epoxy resin liquid, set aside; add isophorone diamine and polyetheramine to a four-necked flask, purge with nitrogen, heat to 50°C, gradually add epoxy resin liquid, control the temperature not to exceed 70°C, add to the flask in about 1 hour, and continue to stir and react at 65-70°C for 1 hour to obtain epoxy curing agent.

[0093] In the two-component epoxy zinc-rich anti-corrosion primer formulation of this invention, conventional additives in the art, such as wetting agents, defoamers, and leveling agents, can also be added. The dosage is the conventional dosage, and technicians can choose to add them according to actual conditions.

[0094] The third objective of this invention is to provide a method for preparing the two-component epoxy zinc-rich anti-corrosion primer described in the second objective of this invention.

[0095] The preparation method of the two-component epoxy zinc-rich anti-corrosion primer includes:

[0096] According to the stated weight proportions, stir each component of component A until homogeneous; according to the stated weight ratio, mix component A and component B and stir until homogeneous.

[0097] The preparation method of component A includes: adding modified epoxy resin and dispersant, stirring at 300-500 rpm for 5-10 minutes, adding graphite powder, carbon fiber powder, graphene, and fumed silica, stirring at 800-1200 rpm for 20-30 minutes, adding zinc powder, mica iron oxide, modified barium sulfate, aluminum tripolyphosphate, and anti-rust pigment, stirring at 800-1200 rpm for 30-40 minutes until no particles are present, adding organic bentonite, stirring at 800-1200 rpm for 20-30 minutes, filtering, and obtaining component A.

[0098] The application method of the two-component epoxy zinc-rich anti-corrosion primer includes: first, stirring the two components of component A separately until they are evenly mixed, then mixing components A and B, stirring evenly, adding an appropriate amount of solvent to dilute before applying.

[0099] The technical route of this invention is as follows: First, a silane prepolymer containing unsaturated double bonds and alkoxy groups is prepared, then copolymerized with unsaturated monomers to obtain a siloxane-acrylic copolymer resin, and then mixed with liquid epoxy resin to obtain a modified epoxy resin. Compared with existing solvent-based epoxy zinc-rich primers, the advantages of using the modified epoxy resin of this invention to prepare epoxy zinc-rich primers are: the coupling groups in the modified resin can form covalent bonds with the substrate, significantly improving the dry and wet adhesion of the zinc-rich primer to the substrate; the use of a copolymer of coupling agent monomer and acrylic monomer to modify the epoxy resin results in better system compatibility compared with formulations that directly add silane coupling agent prepolymers, and the resulting epoxy zinc-rich primer has stronger adhesion and better anti-corrosion performance.

[0100] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0101] When the modified epoxy resin prepared in this invention is used as a base material for zinc-rich primer, the pre-hydrolyzed siloxane groups in the silicate-acrylic copolymer significantly improve the dry and wet adhesion of the coating to the substrate; the resulting zinc-rich primer has a solid content of more than 95%, which significantly reduces the VOC content of the zinc-rich primer.

[0102] This invention relates to a two-component epoxy zinc-rich primer. Component A uses a silicate-acrylic copolymer modified epoxy resin as a base material, and adds zinc powder, graphite powder, carbon fiber, graphene, physical rust-inhibiting pigments, and chemical rust-inhibiting pigments. Component B is a polyetheramine and ester-cyclic amine epoxy resin adduct curing agent. The pre-hydrolyzed siloxane groups in the silicate-acrylic copolymer significantly improve the dry and wet adhesion of the coating to the substrate. The addition of graphite powder, carbon fiber, and graphene reduces the amount of zinc powder required, and the combined use of graphite powder, carbon fiber, and graphene significantly reduces costs compared to using graphene alone. The use of physical and chemical rust-inhibiting pigments ensures that the paint film continues to have excellent shielding ability even after the zinc powder is depleted, greatly extending the anti-corrosion period of the paint film.

[0103] This invention uses a combination of cashew nut shell phenol mono-epoxy reactive diluent, low molecular weight double epoxy reactive diluent, and non-reactive diluent in component A. The combined use of the low molecular weight double epoxy reactive diluent, cashew nut shell phenol mono-epoxy reactive diluent, and non-reactive diluent, utilizing the hydrophobicity of the cashew nut shell phenol group and the viscosity-reducing effect of the non-reactive diluent, can reduce the viscosity of the epoxy resin without significantly reducing its anti-corrosion performance, thereby reducing solvent usage and lowering the VOC content of the zinc-rich primer. This solves the problem that using low molecular weight reactive diluent alone would greatly reduce the anti-corrosion performance of the paint film.

[0104] The high-solids epoxy zinc-rich primer of the present invention has the characteristics of strong adhesion, good flexibility and excellent salt spray performance; it can replace epoxy zinc-rich primer with high zinc powder content as a pre-coating primer and zinc-rich primer for shipbuilding and railway vehicle production, or as a heavy-duty anti-corrosion coating for anti-corrosion coating of steel structures in bridges and petrochemical enterprises. Detailed Implementation

[0105] The present invention will now be described in detail with reference to specific 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.

[0106] All reagents used in the following examples are commercially available products. The sources of each raw material are as follows:

[0107] 560 silane coupling agent, sourced from Wuhan Anruike Materials Co., Ltd.;

[0108] 570 silane coupling agent, sourced from Wuhan Anruike Materials Co., Ltd.;

[0109] Tetraethyl silicate, sourced from Jinan Shuangying Chemical Co., Ltd.;

[0110] Dimethyl methyl phenyl silicate, sourced from Anhui Mingyi Silicon Industry Co., Ltd.

[0111] The ethanol comes from Jinan Shuangying Chemical Co., Ltd.

[0112] D001*7 resin, sourced from Shanghai Kaiping Resin Co., Ltd.;

[0113] Styrene, sourced from Qilu Petrochemical Co., Ltd.;

[0114] Butyl acrylate, sourced from Wanhua Chemical Group Co., Ltd.;

[0115] Benzoyl peroxide, sourced from Shandong Ketian Chemical Co., Ltd.

[0116] Propylene glycol methyl ether, sourced from Jiangsu Sanmu Group Co., Ltd.;

[0117] Tripropylene glycol butyl ether, from Dow Chemical Company;

[0118] E-51 epoxy resin is from Bluestar Nantong Xingchen Synthetic Materials Co., Ltd.

[0119] E-44 epoxy resin is from Lanxing Nantong Xingchen Synthetic Materials Co., Ltd.

[0120] Tripropylene glycol monobutyl ether, from Dow Chemical Company;

[0121] Diethyl phthalate, sourced from Ruentex New Materials Co., Ltd.

[0122] Dibutyl terephthalate, sourced from Shandong Langhui Petrochemical Co., Ltd.;

[0123] Ethylene glycol diglycidyl ether, sourced from Anhui Hengyuan Chemical Co., Ltd.;

[0124] Cashew phenol glycidyl ether, from Cardley Chemicals Ltd.;

[0125] C12-14 alkyl glycidyl ether, sourced from Baling Petrochemical Co., Ltd.;

[0126] Isophorone diamine, sourced from Wanhua Chemical Group Co., Ltd.;

[0127] D-230 polyetheramine is from Shandong Tonglan Chemical Co., Ltd.

[0128] Graphene, from Yuanfeng Chemical Co., Ltd.;

[0129] Carbon fiber powder, sourced from Toray Industries, Inc.

[0130] Graphite powder, from Nanshu Graphite Mine;

[0131] The dispersant is from Hemings Technology Co., Ltd.

[0132] Zinc powder, sourced from Hunan Xinweiling Metal New Materials Co., Ltd.

[0133] Mica iron oxide, sourced from Jinan Huijinchuan Chemical Co., Ltd.;

[0134] Modified barium sulfate, sourced from Jiangsu Qunxin Powder Technology Co., Ltd.

[0135] Aluminum tripolyphosphate, sourced from Guangxi Chemical Research Institute;

[0136] Composite zinc silicate, sourced from Shanghai Xinjing Chemical Co., Ltd.;

[0137] Organic bentonite, from Haimings Technology Co., Ltd.

[0138] Fumed silica, from Evonik Chemicals Ltd.

[0139] Examples 1-5

[0140] Preparation of silane prepolymers:

[0141] In a four-necked flask, tetraethyl silicate, dimethyl methyl phenyl silicate, 560 silane coupling agent, 570 silane coupling agent, ethanol, and ion exchange resin were added and stirred for 5 minutes. Stirring continued, with deionized water added dropwise over 1.5 hours. After the addition was complete, stirring continued for another 1.5 hours. The mixture was allowed to stand for 24 hours, then filtered through a 120-mesh screen to obtain the silane prepolymer. The stirring speed was 60 rpm.

[0142] Among them, the silicate ester prepolymers prepared in Examples 1-5 are silane prepolymers S1-S5, respectively. The appearance of silane prepolymers S1-S5 is "uniform and transparent".

[0143] The raw material formulas used in Examples 1-5 are shown in Table 3. In Table 3, the unit for each raw material is g.

[0144] Table 3

[0145]

[0146] Examples 6-10

[0147] Preparation of silane-acrylic acid copolymer:

[0148] ① Add propylene glycol methyl ether and tripropylene glycol butyl ether to the reaction vessel and heat to a gentle boil.

[0149] ② Keep boiling gently, add one-fifth styrene, one-fifth butyl acrylate, and one-third initiator, and keep warm for 20 minutes.

[0150] ③ Maintain a gentle boil and gradually add the mixture consisting of the remaining styrene, butyl acrylate, initiator, and silane prepolymer dropwise over 1.5 hours. After the addition is complete, continue to maintain the temperature for 1 hour to obtain the silane-acrylic acid copolymer.

[0151] Among them, the silane-acrylic acid copolymers prepared in Examples 6-10 are silane-acrylic acid copolymers AS1-AS5, respectively.

[0152] The raw material formulas used in Examples 6-10 are shown in Table 4. In Table 4, the unit for each raw material is g.

[0153] Table 4

[0154]

[0155] Examples 11-15

[0156] Preparation of modified epoxy resin:

[0157] Liquid epoxy resin, non-reactive diluent, and reactive diluent are added to a stirring container equipped with a heating device, heated to 60°C, and stirred for 1 hour; silane acrylic acid prepolymer is added, and stirred for 0.5 hours; modified epoxy resin is obtained.

[0158] Among them, the modified epoxy resins prepared in Examples 11-15 are modified epoxy resins E1-E5, respectively.

[0159] The raw material formulas used in Examples 11-15 are shown in Table 5. In Table 5, the unit for each raw material is g.

[0160] Table 5

[0161]

[0162] Examples 16-21

[0163] Preparation of Component A of a two-component epoxy zinc-rich anti-corrosion primer:

[0164] Add modified epoxy resin and dispersant to a mixing container and stir at low speed (300 rpm) for 5 minutes; add graphite, carbon fiber powder, graphene, and fumed silica and disperse at high speed (800 rpm) for 30 minutes; add zinc powder, mica iron oxide, modified barium sulfate, aluminum tripolyphosphate, and composite zinc silicate and stir at high speed (800 rpm) for 30 minutes; add organic bentonite and stir at high speed (800 rpm) for 30 minutes; filter with a 100-mesh stainless steel screen to obtain epoxy graphene zinc powder slurry (component A).

[0165] The raw material formulations used in Examples 16-21 are shown in Table 6. In Table 6, the unit for each raw material is g.

[0166] Table 6

[0167]

[0168] Examples 22-26

[0169] Preparation of epoxy curing agent:

[0170] E51 epoxy resin, propylene glycol methyl ether, and propylene glycol ethyl ether were added to a flask and stirred to dissolve, yielding an epoxy resin solution. Isophorone diamine and ED-600 polyetheramine were added to a four-necked flask, nitrogen gas was introduced, and the mixture was heated to 50°C. E51 epoxy resin was gradually added, maintaining the temperature at 65°C, for approximately 1 hour. After the addition was complete, the mixture was kept at 65°C and stirred for another 1 hour to obtain the epoxy curing agent (component B).

[0171] Among them, the epoxy curing agents prepared in Examples 22-26 are epoxy curing agents H1-H5, respectively.

[0172] The raw material formulas used in Examples 22-26 are shown in Table 7. In Table 7, the unit for each raw material is g.

[0173] Table 7

[0174]

[0175] Examples 27-32

[0176] Preparation of a two-component epoxy zinc-rich anti-corrosion primer:

[0177] Mix components A and B according to the specified ratio, stir for 3 minutes, let stand for 5 minutes, and then add epoxy diluent.

[0178] The components A and B used in Examples 27-32 and their amounts are shown in Table 8. In Table 8, the unit for each raw material is g.

[0179] Table 8

[0180]

[0181] Comparative Examples 1-2

[0182] Component A: Add epoxy resin and dispersant to a mixing container and stir at low speed (300 rpm) for 5 minutes; add zinc powder, mica iron oxide, modified barium sulfate, aluminum tripolyphosphate, and ferric phosphorus powder, and disperse at high speed (800 rpm) for 30 minutes; add fumed silica and organobentonite, and stir at high speed (300 rpm) for 30 minutes; filter with a 100-mesh stainless steel screen to obtain component A.

[0183] Component B: Add polyamide 300, xylene, and n-butanol, and stir component A at low speed for 5 minutes to obtain component B.

[0184] Mix components A and B according to the specified ratio, stir for 3 minutes, let stand for 5 minutes, and then add epoxy diluent to adjust the viscosity.

[0185] The components A and B used in Examples 27-32 and their amounts are shown in Table 9. In Table 9, the unit for each raw material is g.

[0186] Table 9

[0187]

[0188] Performance testing

[0189] The zinc-rich coatings of Examples 27-32 and the zinc-rich coatings of Comparative Examples 1 and 2 were subjected to performance tests as shown in Table 10. The test results are shown in Tables 11 and 12.

[0190] Workability and coating appearance: After mixing the two components, dilute with 5% solvent and apply using a wool or nylon brush, or dilute with 3% solvent and spray using a high-pressure airless sprayer. Examine the smoothness of application, wet film sagging, leveling, bubbles, dry film color, brush marks, orange peel, pinholes, cracks, and other defects.

[0191] Standard performance: Apply one coat of tinplate with a thickness of 20-30μm on a 7×150×0.25mm sheet.

[0192] Salt spray test: Apply two coats of salt spray to a 7×150×1 cold-rolled steel sheet, with a thickness of 60-80μm.

[0193] Drying method: For the appearance of the coating, dry at room temperature for 15 minutes, then dry at 50-70℃ for 30 minutes; for other performance tests of the coating, dry at 23±2℃ and relative humidity for 7 days.

[0194] Table 10

[0195]

[0196] Table 11

[0197]

[0198] Table 12

[0199]

[0200] As can be seen from the data in Table 11, the salt spray resistance of the paint film decreases with the reduction of the dry film zinc powder content in the formulations of Examples 27-32 of this invention. However, the salt spray resistance of the waterborne epoxy zinc-rich primer with a dry film zinc powder content of 26.1% (Example 32) also meets the index of zinc-rich primer with a dry film zinc powder content of 70% in the HG / T 3668-2020 standard.

[0201] Comparative Examples 1 and 2 in Table 12 used traditional epoxy zinc-rich primer formulations. The matrix resin of the zinc powder paste component was E44 epoxy resin, diluted with xylene and n-butanol to achieve a suitable viscosity. The curing agent in component B was polyamide No. 300. The VOC content of the comparative examples reached over 10%. Comparative Example 1 had a zinc powder dry film content of 40%, and its salt spray test results were inferior to Example 32, which had a dry film zinc powder content of 26%. Comparative Example 2 had a zinc powder dry film content of 69%, and its salt spray test results were inferior to Example 31, which had a dry film zinc powder content of 29%.

[0202] Compared with Comparative Examples 1-2, Examples 27-32 showed a 7.2-8.4% increase in solid content, a 7.2-8.4% decrease in VOC content, a 50-125 μm improvement in anti-sagging properties, a 16-83% increase in adhesion, and a significant improvement in salt spray resistance. Therefore, compared to existing zinc-rich primers that use conventional epoxy resins as the main film-forming material, this invention, using a self-made modified epoxy resin as the main film-forming material, solves the technical problem that "existing solvent-based zinc-rich primers typically contain a large amount of organic solvents and have a high VOC content for ease of spraying."

[0203] Compared to Comparative Example 2, the zinc content (dry film) of Examples 27-31 decreased by 17.5-39.9%. Compared to Comparative Example 1, the solid content of Examples 27-31 increased by 7.2-8.4%, the VOC content decreased by 7.2-8.4%, the anti-sagging property improved by 50-125 μm, the adhesion improved by 14-57%, and the salt spray resistance was also significantly improved. This indicates that the zinc-rich primer of the present invention not only reduces the zinc content but also significantly improves its corrosion resistance. Therefore, the present invention solves the problems of existing zinc-rich primers where "reducing the zinc powder content leads to a rapid decline in its anti-corrosion performance" and "graphene has a very large specific surface area, making it difficult to wet and disperse in the primer, thus hindering the effective application of anti-corrosion performance" by using a self-made modified epoxy resin as the main film-forming substance and adding graphene, graphite powder, and carbon fiber powder.

Claims

1. A two-component epoxy zinc-rich anti-corrosion primer, characterized in that, The two-component epoxy zinc-rich anti-corrosion primer is composed of component A and component B in a weight ratio of 7-10:

1. Component A includes: 100 parts by weight of modified epoxy resin; Graphene 1-8 parts by weight; 3-30 parts by weight of carbon fiber powder; 10-90 parts by weight of graphite powder; Dispersant 3-10 parts by weight; 200-500 parts by weight of zinc powder; 50-200 parts by weight of mica iron oxide; Modified barium sulfate, 20-200 parts by weight; 20-60 parts by weight of aluminum tripolyphosphate; 50-200 parts by weight of anti-rust pigment; 5-15 parts by weight of organic bentonite; 2-8 parts by weight of fumed silica; Component B is an epoxy curing agent; The modified epoxy resin is prepared by stirring a raw material containing the following components at 50-60°C for 0.5-1 h; the components and their weight parts are as follows: 100 parts by weight of liquid epoxy resin; 10-30 parts by weight of silane-acrylic acid copolymer; 5-20 parts by weight of non-reactive diluent; 5-20 parts by weight of reactive diluent; The silane-acrylic acid copolymer is prepared from raw materials comprising the following components; the components and their parts by weight are as follows: 100 parts by weight of unsaturated monomer; 10-25 parts by weight of silane prepolymer; Initiator 1-3 parts by weight; 2.5-10 parts by weight of propylene glycol methyl ether; 2.5-10 parts by weight of tripropylene glycol butyl ether; The silane prepolymer is prepared from raw materials comprising the following components; the components and their parts by weight are as follows: 100 parts by weight of silane coupling agent; 50-150 parts by weight of silicate; 20-40 parts by weight of propylene glycol methyl ether; 4-10 parts by weight of ion exchange resin; 8-20 parts by weight of deionized water; The method for preparing the silane prepolymer includes: stirring silicate ester, silane coupling agent, propylene glycol methyl ether, and ion exchange resin at low speed for 5-10 minutes at 60-65°C; adding deionized water dropwise while continuing to stir, completing the addition within 1-1.5 hours; continuing to stir for 1-1.5 hours after the addition is complete; and allowing it to stand for more than 12 hours to obtain the silane prepolymer; the low speed is 50-100 rpm. The epoxy curing agent is prepared from raw materials containing the following components; the components and their weight parts are as follows: 100 parts by weight of epoxy resin; 20-40 parts by weight of propylene glycol methyl ether; 30-50 parts by weight of propylene glycol ethyl ether; Isophorone diamine 20-80 parts by weight; 20-100 parts by weight of polyetheramine; The preparation method of the epoxy curing agent includes: dissolving epoxy resin in propylene glycol methyl ether and propylene glycol ethyl ether to obtain an epoxy resin liquid; heating isophorone diamine and polyetheramine in a nitrogen atmosphere to 50-70°C, adding the epoxy resin liquid, and continuing to stir and react at 65-70°C for 1-1.5 hours to obtain the epoxy curing agent; the epoxy resin liquid is added completely in 1-1.5 hours.

2. The two-component epoxy zinc-rich anti-corrosion primer as described in claim 1, characterized in that, The weight ratio of component A to component B is 9-10:

1.

3. The two-component epoxy zinc-rich anti-corrosion primer as described in claim 1, characterized in that, Component A includes: 100 parts by weight of modified epoxy resin; Graphene 1-6 parts by weight; 15-25 parts by weight of carbon fiber powder; 30-90 parts by weight of graphite powder; Dispersant 3-10 parts by weight; 200-400 parts by weight of zinc powder; 60-150 parts by weight of mica iron oxide; Modified barium sulfate, 30-100 parts by weight; 25-50 parts by weight of aluminum tripolyphosphate; 80-150 parts by weight of anti-rust pigment; 8-12 parts by weight of organic bentonite; 3-5 parts by weight of fumed silica.

4. The two-component epoxy zinc-rich anti-corrosion primer as described in claim 1, characterized in that, The modified epoxy resin is prepared from raw materials containing the following components; the components and their parts by weight are as follows: 100 parts by weight of liquid epoxy resin; 15-25 parts by weight of silane-acrylic acid copolymer; 8-15 parts by weight of non-reactive diluent; 8-15 parts by weight of reactive diluent.

5. The two-component epoxy zinc-rich anti-corrosion primer as described in claim 1, characterized in that, The liquid epoxy resin is a bisphenol A type liquid epoxy resin; or / and The inactive diluent is selected from one or more of tripropylene glycol butyl ether, diethyl phthalate, dibutyl phthalate, dioctyl terephthalate, tributyl acetyl citrate, dodecyl alcohol ester, and hexadecyl alcohol ester; or / and, The active diluent is selected from one or more of ethylene glycol diglycidyl ether, cashew phenol glycidyl ether, and C12-C14 alkyl glycidyl ether.

6. The two-component epoxy zinc-rich anti-corrosion primer as described in claim 1, characterized in that, The silane-acrylic acid copolymer is prepared from raw materials comprising the following components; the components and their parts by weight are as follows: 100 parts by weight of unsaturated monomer; 12-20 parts by weight of silane prepolymer; Initiator 1.5-2.5 parts by weight; 4-8 parts by weight of propylene glycol methyl ether; 4-8 parts by weight of tripropylene glycol butyl ether.

7. The two-component epoxy zinc-rich anti-corrosion primer as described in claim 1, characterized in that, The unsaturated monomer is selected from one or more of styrene, methyl methacrylate, methyl acrylate, glycidyl acrylate, butyl acrylate, and octyl acrylate; or / and, The initiator is selected from one or more of benzoyl peroxide, tert-butyl peroxide, and dicumyl peroxide.

8. The two-component epoxy zinc-rich anti-corrosion primer as described in claim 1, characterized in that, The silane prepolymer is prepared from the following raw materials; the components and their parts by weight are as follows: 100 parts by weight of silane coupling agent; 80-120 parts by weight of silicate; 25-35 parts by weight of propylene glycol methyl ether; 5-8 parts by weight of ion exchange resin; 10-15 parts by weight of deionized water.

9. The two-component epoxy zinc-rich anti-corrosion primer as described in claim 1, characterized in that, The silane coupling agent is selected from one or more of methacryloyloxypropyltrimethoxysiloxane, methacryloyloxypropyltriethoxysiloxane, vinyltriethoxysilane, vinyltrimethoxysilane, and vinyltris(β-methoxyethoxy)silane; or / and, The silicate ester is selected from one or more of tetraethyl silicate, dimethyl methylphenyl silicate, and diethyl diphenyl silicate; or / and, The ion exchange resin is a strongly acidic ion exchange resin.

10. The two-component epoxy zinc-rich anti-corrosion primer as described in claim 1, characterized in that, The epoxy curing agent is prepared from raw materials containing the following components; the components and their weight parts are as follows: 100 parts by weight of epoxy resin; 22-31 parts by weight of propylene glycol methyl ether; 35-45 parts by weight of propylene glycol ethyl ether; 30-70 parts by weight of isophorone diamine; 30-80 parts by weight of polyetheramine.

11. The two-component epoxy zinc-rich anti-corrosion primer as described in claim 1, characterized in that, The epoxy resin is a bisphenol A type liquid epoxy resin; The polyetheramine is an amino-terminated polyether with a molecular weight range of 200-600.

12. The two-component epoxy zinc-rich anti-corrosion primer as described in claim 1, characterized in that, The graphene is a reduced multilayer graphene.

13. The two-component epoxy zinc-rich anti-corrosion primer as described in claim 1, characterized in that, The graphene contains ≥99% carbon; or / and, The graphene has a particle size of 1-20 μm; or / and, The thickness of the graphene is 3-30 nm; or / and, The carbon fiber powder has a mesh size of 200-1500 mesh; or / and, The carbon fiber powder has a fiber diameter of 5-10 μm; or / and, The graphite powder is flake-shaped graphite powder; or / and, The graphite powder has a mesh size of 200-3000 mesh.

14. The two-component epoxy zinc-rich anti-corrosion primer as described in claim 1, characterized in that, The graphene has a particle size of 2-10 μm; or / and, The thickness of the graphene is 5-15 nm; or / and, The carbon fiber powder has a mesh size of 400-800 mesh; or / and, The graphite powder has a mesh size of 400-1200.

15. A method for preparing a two-component epoxy zinc-rich anti-corrosion primer as described in any one of claims 1-14, characterized in that, The preparation method includes: According to the stated weight proportions, the components of component A are stirred evenly; according to the stated weight ratio, components A and B are mixed and stirred evenly to obtain the two-component epoxy zinc-rich anti-corrosion primer.

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