Thick-film self-laminating water-based epoxy graphene heavy-duty anticorrosive coating and preparation method thereof

Abstract

This invention discloses a thick-film, self-layering waterborne epoxy graphene heavy-duty anti-corrosion coating. The coating uses waterborne epoxy emulsion and waterborne fluorocarbon resin as the main film-forming materials, combined with a composite dispersion slurry of graphene oxide and nano-zinc oxide, and employs a special polyurea-modified wax as a rheology modifier. Utilizing the low surface energy of the waterborne fluorocarbon resin, the coating automatically layers during curing to form a "bottom-protected, top-resistant" structure; simultaneously, the layered structure of graphene and the synergistic effect of nano-zinc oxide construct a dense physical shielding layer. This invention solves the industry problem of easy bubbling in thick-film waterborne epoxy coatings, achieving a single coating with both high salt spray resistance (≥2000h) and UV aging resistance (≥1000h), making it suitable for harsh corrosive environments such as offshore platforms and cross-sea bridges.

Description

Technical Field

[0001] This invention belongs to the field of waterborne industrial coatings technology, specifically relating to a high-performance waterborne anti-corrosion coating suitable for marine engineering, petrochemical storage tanks and bridge steel structures, and in particular an epoxy / acrylic hybrid coating that can be applied in a single thick coat and form a self-layered structure. Background Technology

[0002] With increasingly stringent environmental regulations, the shift from oil-based to water-based coatings has become an inevitable trend in the industrial corrosion protection field. However, existing water-based industrial paints face three major technical bottlenecks in heavy-duty corrosion protection: 1. Poor performance with thick coatings: Traditional water-based paints have limited film thickness (usually ≤80μm) when applied in a single coat. If the coating is too thick in one application, the film is prone to "wet film adhesion" or "bubbling" after drying due to poor water evaporation; 2. The contradiction between early water resistance and later salt spray resistance: Water-based epoxy requires the introduction of hydrophilic groups to ensure stability, resulting in weak early water erosion resistance of the film before complete cross-linking; at the same time, to ensure long-term corrosion protection (>1000h salt spray resistance), a large amount of heavy metal rust-inhibiting fillers such as strontium chromate yellow are often added; 3. Limited functionality: Conventional primers only have anti-corrosion function, while topcoats provide weather resistance. On-site application requires a combination of primer and topcoat, which is inefficient. Summary of the Invention

[0003] The present invention aims to provide a thick-film, self-layering, waterborne epoxy graphene heavy-duty anti-corrosion coating.

[0004] This invention achieves the following breakthroughs through a "one-agent-multi-functional" compounding technology: 1. By using modified amine emulsion and special rheology modifiers, the volume solids content of the coating reaches over 60%, supporting a dry film thickness of 150-200μm with no sagging or bubbling after a single spraying; 2. By introducing a graphene / nano zinc oxide composite slurry stabilized by a nonionic emulsifier, utilizing the "maze effect" of graphene and the cathodic protection of nano zinc oxide, a highly efficient conductive shielding network is constructed at a low addition amount (<0.5%); by introducing waterborne fluorocarbon resin / acrylic resin blend modification, utilizing the surface energy difference, the coating automatically layers during the curing process: the bottom layer (epoxy-rich area) provides adhesion and corrosion resistance, while the top layer (fluorocarbon-rich area) provides hydrophobicity and weather resistance. Detailed implementation method: This embodiment details the application of the coating in a marine atmospheric environment (C5-M environment).

[0005] Step 1: Preparation of modified graphene / nano zinc oxide slurry Take 1g of graphene oxide (Changzhou Sixth Element) and 2g of nano zinc oxide (Nanjing Epuri), add them to a solution containing 0.5g of BYK-190 dispersant and 20g of deionized water while stirring, grind with zirconium beads for 2 hours, and filter for later use.

[0006] Step 2: Preparation of Component A Add the following to the reactor according to the following weight proportions: Deionized water: 20.0 parts Dispersant (BYK-190): 1.2 parts Defoamer (BYK-024): 0.3 parts Propylene glycol methyl ether: 2.0 parts Dipropylene glycol butyl ether: 3.0 parts Titanium dioxide (R-996): 10.0 parts Aluminum tripolyphosphate (APW-II): 12.0 parts Modified graphene / nano zinc oxide slurry: 8.0 parts Precipitated barium sulfate: 10.0 parts After mixing thoroughly, grind to a fineness ≤30μm. Then add: Waterborne epoxy emulsion (EPIKOTE 7520-WD-52A): 30.0 parts Waterborne fluorocarbon emulsion (F500, Daikin Japan): 15.0 parts Substrate wetting agent (Tego 2800): 0.5 parts Thickener (RM-8W): 0.8 parts Polyurea rheology modifier (BYK-420): 1.0 part Stir and disperse evenly to obtain component A.

[0007] Step 3: Preparation of Component B Mix in another container: Water-based epoxy curing agent (Anquamine 721): 90.0 parts Anti-flash rust agent (Raybo 60): 4.0 parts Fungicide (MV): 0.2 parts Mix thoroughly to obtain component B. The A:B mixing ratio is 6:1 (by weight).

[0008] Performance testing The prepared coating was sprayed onto a sandblasted steel plate (Sa2.5 grade), with the dry film thickness controlled at 150±20μm. After curing at room temperature for 7 days, the coating was tested. 1. Drying performance: Surface dry ≤ 25 minutes; Complete dry ≤ 4 hours. Baking at 80℃ for 30 minutes is sufficient before removal from production line and handling. 2. Adhesion: Pull-off test > 8 MPa (pull-off test, C81-88 standard); 3. Salt spray resistance: According to GB / T 1771-2007 standard, the single-item corrosion at the scribed area is ≤2mm, and there is no blistering or rust in the unscribed area (test time 2000 hours). 4. Weather resistance: After 1000 hours of QUV-B (313nm) aging test, the gloss retention rate is ≥80%, and there is no chalking; 5. Thick coating anti-sagging: Using airless spraying (nozzle diameter 0.48mm), a 300μm wet film is sprayed in one go. After drying, there is no sagging or micro-bubbling.

Claims

1. A thick-film, self-layering, waterborne epoxy graphene heavy-duty anti-corrosion coating, characterized in that, It is composed of component A and component B mixed in a mass ratio of (3-8):1; Component A (color paint paste) comprises, by weight, the following: Waterborne epoxy resin (epoxy equivalent 500-700): 25-35 parts Waterborne fluorocarbon emulsion (F content > 10%): 10-20 parts Modified graphene / nano zinc oxide composite dispersion: 5-10 parts Rust-inhibiting pigment (aluminum tripolyphosphate / zinc phosphate mixture): 15-25 parts Sericite powder / talc powder (filler): 10-15 parts Cosolvent (dipropylene glycol butyl ether / propylene glycol methyl ether): 3-6 parts Wetting and dispersing agent (containing pigment affinity copolymer): 1-2 parts Thixotropic agent (fumed silica / BYK-8421 composite wax paste): 1-3 parts Deionized water: 15-25 parts; Component B (curing agent component) comprises, by weight: Water-based modified amine curing agent (active hydrogen equivalent 250-350): 80-95 parts Anti-flash rust additive (organo-zinc chelate): 3-5 parts Defoamer: 0.5-1 part.

2. The coating according to claim 1, characterized in that, The preparation method of the modified graphene / nano zinc oxide composite dispersion is as follows: Graphene oxide powder (layer thickness <5nm) and zinc oxide nanoparticles (particle size 30-50nm) were mixed at a mass ratio of 1:

2. Add aqueous nonionic dispersant (such as DISPERBYK-190) and high-shear deionized water; Under pH conditions of 8.5-9.5, the material is ground to a fineness D90 < 10 μm using a sand mill to obtain a slurry.

3. The coating according to claim 1, characterized in that, The thixotropic agent is a combination of polyurea-modified polyethylene wax (such as AQUATIX 8421) and hydrophobic-modified alkali-swelling thickener, which enables the paint film to have a high yield value in a wet state and to achieve uniform evaporation of internal moisture under low temperature baking at 80℃ / 30min or air drying at room temperature, thus preventing blistering of thick coatings.

4. The coating according to claim 1, characterized in that, The water-based modified amine curing agent is prepared by block copolymerization of m-phenylenediamine and polyethylene glycol diglycidyl ether, and its solid content is 50±2%. This structure endows the curing agent with self-emulsification function and tolerance to damp surfaces.

5. A method for preparing a thick-film, self-layering, waterborne epoxy graphene heavy-duty anti-corrosion coating as described in any one of claims 1-4, characterized in that... Includes the following steps: (1) Mix deionized water, cosolvent, wetting and dispersing agent, and add pigments, fillers, rust-preventing pigments and composite dispersion slurry under low-speed stirring; (2) After high-speed dispersion, the mixture is transferred to a sand mill and ground to a fineness of ≤30μm to obtain an intermediate slurry; (3) Add the mixture of waterborne epoxy resin and waterborne fluorocarbon emulsion slowly to the intermediate slurry under stirring, and finally add thixotropic agent to adjust the viscosity to 90-110KU, filter and package to obtain component A. (4) During construction, mix component A and component B in proportion, let it mature for 10-15 minutes, add 5-15% deionized water to adjust the construction viscosity, and apply it to the surface of carbon steel substrate by airless spraying.