High-performance anticorrosive paint based on hyperbranched epoxy resin and preparation method of high-performance anticorrosive paint

Abstract

The invention discloses a high-performance anticorrosive paint based on hyperbranched epoxy resin and a preparation method thereof. The coating is a two-component system, wherein a component A comprises glycidyl ether-terminated hyperbranched epoxy resin taking trihydric alcohol as a core, a reactive diluent, a flaky filler, a thixotropic agent and a pigment; and the component B is a curing agent. The core of the invention lies in that the paint has excellent constructability, extremely high adhesive force, flexible cracking resistance and long-acting corrosion resistance by utilizing the unique three-dimensional spherical structure of the hyperbranched epoxy resin and the characteristics of low viscosity and high functionality brought by the hyperbranched epoxy resin. The flaky filler is easy to directionally arrange in the low-viscosity resin and cooperates with the hyperbranched network to form an extreme shielding layer. The coating disclosed by the invention is suitable for metal protection in harsh corrosive environments, such as ships, ocean engineering, chemical equipment and the like.

Description

Technical Field

[0001] This invention relates to the field of polymer materials and metal protection technology, specifically to an anti-corrosion coating with excellent adhesion, corrosion resistance and crack resistance, using hyperbranched epoxy resin as the film-forming material, and its preparation method. Background Technology

[0002] In fields such as petrochemicals, marine engineering, infrastructure construction, and high-end equipment manufacturing, metal substrates face complex operating conditions such as acid and alkali corrosion, salt spray corrosion, and thermal cycling shocks. Anti-corrosion coatings, as a key barrier against corrosion, directly determine the service life and safety stability of the substrate. Epoxy resins, with their strong polarity from the epoxy groups and hydroxyl groups in their molecular chains, exhibit excellent adhesion to metal substrates. Furthermore, the cross-linked structure formed after curing possesses excellent chemical stability and solvent resistance. Therefore, they have long been the core film-forming material for anti-corrosion coatings, holding over 30% of the global anti-corrosion coating market share. However, traditional linear epoxy resins have inherent drawbacks: First, their high viscosity makes high-solids coatings difficult to apply, often requiring large amounts of solvent for dilution, increasing VOC emissions; second, the high cross-linking density and internal stress after curing result in a brittle coating film, easily generating microcracks under thermal cycling or mechanical impact, providing penetration channels for corrosive media; finally, their adhesion to certain special substrates (such as wet surfaces and low surface energy substrates) still needs improvement.

[0003] Hyperbranched polymers possess characteristics such as a three-dimensional spherical structure, numerous terminal functional groups, low viscosity, and high reactivity. Introducing them into epoxy resin systems is an effective way to modify epoxy resins. However, current research on directly using hyperbranched epoxy resins as the main film-forming material in anti-corrosion coatings and utilizing their molecular structure characteristics to systematically address the synergistic improvement of adhesion, internal stress, and barrier properties is insufficient. Existing technologies mostly use them as additives, which suffers from problems such as compatibility, dosage limitations, and insignificant performance improvements.

[0004] Therefore, developing a comprehensive coating with hyperbranched epoxy resin as the main structure that can simultaneously achieve low viscosity, high adhesion, low internal stress, and long-term corrosion protection has significant application value. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a high-adhesion anti-corrosion coating based on hyperbranched epoxy resin with excellent comprehensive performance and its preparation method.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] This invention provides an anti-corrosion coating based on hyperbranched epoxy resin, which is composed of component A and component B in a mass ratio of (4-6):1;

[0008] Component A, by weight, comprises:

[0009] Hyperbranched epoxy resin: 50-80 parts;

[0010] Reactive diluent: 5-15 parts;

[0011] Flake packing: 10-25 parts;

[0012] Thixotropic agent: 1-3 parts;

[0013] Pigment: 0-5 parts;

[0014] Component B is a curing agent, and its dosage is in an equivalent ratio (0.8-1.2):1 with the epoxy groups in component A.

[0015] The hyperbranched epoxy resin has a number-average molecular weight of 2000-10000 g / mol, and its molecular structure is a hyperbranched polyester skeleton with triol as the core and glycidyl ether end capping, and its branching degree is not less than 0.4.

[0016] According to the present invention, the active diluent is one or both of cashew phenol glycidyl ether and neopentyl glycol diglycidyl ether.

[0017] According to the present invention, the sheet-like filler is one or more of mica powder, glass flakes or aluminum hydroxide flakes modified with silane coupling agent, and its aspect ratio is greater than 50.

[0018] According to the present invention, the thixotropic agent is fumed silica or organobentonite.

[0019] According to the present invention, the pigment is one or more of iron oxide red, titanium dioxide, calcium carbonate, and barium sulfate.

[0020] According to the present invention, the curing agent of component B is a modified alicyclic amine curing agent or a phenolic amine curing agent.

[0021] Secondly, the present invention provides a method for preparing the above-mentioned hyperbranched epoxy resin, comprising the following steps:

[0022] S1. Synthesis of Hyperbranched Polyester: Under inert gas protection, a triol core, 2,2-dimethylolpropionic acid, and a catalyst are added to a reaction apparatus equipped with a mechanical stirrer, thermometer, water separator, and reflux condenser. The reaction system is gradually heated under stirring to carry out a melt polycondensation reaction. Water generated during the reaction is promptly separated and discharged through the water separator to obtain terminal hydroxyl hyperbranched polyester alcohol.

[0023] S2. Epoxy end capping: The hyperbranched polyester alcohol obtained in step S1 is dissolved in excess epichlorohydrin, and a phase transfer catalyst is added to the system. The reaction system is heated to a specific temperature, and a 30% to 40% sodium hydroxide aqueous solution is slowly added dropwise under continuous stirring to carry out the epoxidation reaction. After the addition is completed, the reaction is continued at the same temperature to ensure complete end group conversion.

[0024] S3. Post-treatment: After the reaction is complete, the reaction system is allowed to cool naturally to room temperature (approximately 25°C). The reaction product is then repeatedly washed with deionized water until the aqueous phase is neutral (pH≈7). After separating the organic phase, vacuum distillation is performed to recover excess epichlorohydrin. Subsequently, the vacuum level is gradually increased (to below -0.098 MPa) while maintaining the temperature at 70–80°C to thoroughly remove residual moisture and low-boiling-point components, ultimately yielding a light yellow to brownish-yellow, viscous, transparent hyperbranched epoxy resin product.

[0025] According to the present invention, the triol core component in step S1 may be selected from at least one of 1,1,1-trimethylolethane, 1,1,1-trimethylolpropane or glycerol;

[0026] According to the present invention, the 2,2-dimethylolpropionic acid in step S1 is preferably 2,2-dimethylolpropionic acid.

[0027] According to the present invention, the catalyst in step S1 is at least one of p-toluenesulfonic acid, methanesulfonic acid or tetraisopropyl titanate, and its addition amount is 0.5% to 1.5% of the total mass of the monomer.

[0028] According to the present invention, the molar ratio of the triol core to 2,2-dimethylolpropionic acid in step S1 is 1:(6-21).

[0029] According to the present invention, the reaction temperature in step S1 is 120-150°C, and the reaction is maintained within this temperature range for 4-8 hours.

[0030] According to the present invention, the molar ratio of epichlorohydrin to hydroxyl groups in hyperbranched polyester alcohol in step S2 is controlled at (10-15):1.

[0031] According to the present invention, the phase transfer catalyst in step S2 is selected from at least one of tetrabutylammonium bromide, tetraethylammonium bromide or benzyltriethylammonium chloride, and its addition amount is 2% to 5% of the mass of the hyperbranched polyester alcohol.

[0032] According to the present invention, the reaction temperature in step S2 is maintained at 60-80°C and the reaction time is 2-4 hours.

[0033] According to the present invention, the molar ratio of sodium hydroxide to hydroxyl groups in hyperbranched polyester alcohol in step S2 is (1.05~1.15):1.

[0034] Thirdly, the present invention provides a method for preparing the above-mentioned anti-corrosion coating, comprising the following steps:

[0035] (a) Add the formulated amount of hyperbranched epoxy resin and reactive diluent into a dispersion tank, stir at low speed until uniform, then add thixotropic agent, flake filler and pigment in sequence, and disperse at high speed (1000-1500 rpm) for 20-40 minutes.

[0036] (b) Transfer the mixture to a sand mill and grind it to a fineness of ≤30μm, then discharge and package it as component A.

[0037] (c) Mix component A and component B evenly in proportion, and apply after curing for 10 to 20 minutes.

[0038] According to the present invention, the specific amount of each component added in component A of the anti-corrosion coating in step (a) is as follows, in parts by weight:

[0039] Hyperbranched epoxy resin: 50-80 parts;

[0040] Reactive diluent: 5-15 parts;

[0041] Flake packing: 10-25 parts;

[0042] Thixotropic agent: 1-3 parts;

[0043] Pigment: 0-5 parts;

[0044] According to the present invention, the active diluent is one or both of cashew phenol glycidyl ether and neopentyl glycol diglycidyl ether.

[0045] According to the present invention, the sheet-like filler is one or more of mica powder, glass flakes or aluminum hydroxide flakes modified with silane coupling agent, and its aspect ratio is greater than 50.

[0046] According to the present invention, the thixotropic agent is fumed silica or organobentonite.

[0047] According to the present invention, the curing agent of component B is a modified alicyclic amine curing agent or a phenolic amine curing agent.

[0048] According to the present invention, the pigment is one or more of iron oxide red, titanium dioxide, calcium carbonate, and barium sulfate.

[0049] According to the present invention, the component B in step (c) is a curing agent, and the mass ratio of component B to component A is 1:(4-6). This ratio is determined based on the epoxy value of the hyperbranched epoxy resin and the amine value of the selected curing agent, according to the equivalent ratio of epoxy groups to active hydrogen of (0.8-1.2):1.

[0050] The beneficial effects of this invention are as follows:

[0051] Low viscosity and high adhesion: The three-dimensional spherical structure of hyperbranched epoxy resin gives it a viscosity far lower than that of linear epoxy resins of similar molecular weight. This not only allows for the formulation of high-solids, low-VOC coatings, but also gives it excellent wetting and penetration capabilities to the substrate. The numerous epoxy groups at the ends of its molecules can form denser chemical bonds and physical adsorption with the substrate surface, thereby achieving extremely high adhesion (up to grade 0).

[0052] Low internal stress and high toughness: The non-entangled structure of hyperbranched molecules and the large number of end groups effectively release stress during curing, significantly reducing the curing shrinkage and internal stress of the coating. This allows the coating to maintain a high crosslinking density while also possessing good flexibility and impact resistance, making it less prone to cracking due to deformation or temperature changes.

[0053] Synergistic shielding effect: This invention utilizes the low viscosity of hyperbranched epoxy resin, enabling it to fully coat and wet high-content sheet fillers. These oriented sheet fillers, in synergy with the dense cross-linked network of the hyperbranched resin, construct a "maze-like" ultra-strong shielding layer, greatly delaying the penetration of corrosive media.

[0054] Construction and environmental advantages: The resin itself has low viscosity, reducing reliance on volatile solvents, making construction easier and more environmentally friendly. The coating has a long pot life, high coverage, and good overall economic benefits. Detailed Implementation

[0055] The present invention will be further described below with reference to embodiments. It should be noted that the following embodiments are not intended to limit the scope of protection of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0056] Example 1:

[0057] (1) Synthesis of hyperbranched epoxy resin

[0058] Step S1: In a 500 mL four-necked flask equipped with a mechanical stirrer, thermometer, nitrogen inlet, and water separator, add 1,1,1-trimethylolpropane (core material, 13.42 g, 0.10 mol), 2,2-dimethylolpropionic acid (2,2-dimethylolpropionic acid, 107.10 g, 0.80 mol), and p-toluenesulfonic acid (catalyst, 0.90 g, approximately 0.75% of the total monomer mass). Purge the air with high-purity nitrogen and maintain a slight positive pressure (approximately 0.02 MPa) for protection. Start stirring and slowly raise the temperature to 135 °C to initiate a melt polycondensation reaction. The reaction continues for approximately 5 hours, during which water generated is removed using the water separator. Stop the reaction when the acid value of the system drops to 3.5 mg KOH / g, yielding a third-generation (G3) terminally hydroxyl hyperbranched polyester alcohol, a light yellow viscous liquid.

[0059] Step S2: Dissolve the obtained hyperbranched polyester alcohol (approximately 100 g, or approximately 0.75 mol OH based on hydroxyl groups) in epichlorohydrin (400 mL, approximately 4.8 mol), and add tetrabutylammonium bromide (phase transfer catalyst, 3.0 g, approximately 3% of the polyester alcohol mass). Maintain the system temperature at 70°C and continue stirring. Slowly add 90 g (approximately 0.79 mol) of a 35% sodium hydroxide aqueous solution over 1.5 hours. After the addition is complete, continue the reaction at 70°C for 3 hours.

[0060] Step S3: After cooling the reaction solution to room temperature, transfer it to a separatory funnel and wash three times with deionized water until the aqueous phase is neutral (pH = 7). Separate the organic phase. First, perform vacuum distillation at 70℃ and -0.092 MPa to recover excess epichlorohydrin. Then, increase the vacuum to above -0.098 MPa and raise the temperature to 75℃ to continue removing residual water for 1 hour, yielding 115 g of a light yellow, transparent, viscous resin product. The epoxy value of this hyperbranched epoxy resin was determined to be 0.58 eq / 100 g, with a yield of 89%.

[0061] (2) Preparation of anti-corrosion coatings

[0062] Step S1: Take 60 parts of the above hyperbranched epoxy resin and 10 parts of cashew phenol glycidyl ether and put them into a dispersion tank, stirring at low speed. Add 2 parts of fumed silica, 20 parts of silane-modified glass flakes, and 3 parts of titanium dioxide, and disperse at high speed for 30 minutes. Grind to a fineness of 25 μm and discharge.

[0063] Step S2: Select a modified alicyclic amine curing agent (amine value 240mg KOH / g) and mix component A and component B at a mass ratio of 5:1.

[0064] Example 2:

[0065] (1) Synthesis of hyperbranched epoxy resin

[0066] Step S1: The apparatus is the same as in Example 1. 1,1,1-Trimethylolethane (core, 12.01 g, 0.10 mol) and 2,2-dimethylolpropionic acid (2,2-dimethylolpropionic acid, 133.88 g, 1.00 mol), as well as the catalyst methanesulfonic acid (1.17 g, approximately 0.80% of the total monomer mass), are added. Under nitrogen protection, the reaction temperature is raised to 145°C, and the reaction is carried out for approximately 6 hours until the acid value drops to 4.2 mg KOH / g, yielding a higher-generation hyperbranched polyester alcohol.

[0067] Step S2: Dissolve the obtained polyester alcohol in excess epichlorohydrin (450 mL) and add benzyltriethylammonium chloride (phase transfer catalyst, 4.5 g, approximately 4% of the polyester alcohol mass). At 65°C, slowly add 86 g (approximately 0.86 mol) of a 40% sodium hydroxide aqueous solution over 2 hours. After the addition is complete, continue the reaction at 65°C for 2.5 hours.

[0068] Step S3: After cooling, wash with water until neutral. The organic phase is distilled at 65℃ and -0.090 MPa to recover epichlorohydrin, then dried at 78℃ and -0.1 MPa to obtain 138 g of a brownish-yellow transparent resin product. The epoxy value was determined to be 0.51 eq / 100 g, with a yield of 86%.

[0069] (2) Preparation of anti-corrosion coatings

[0070] Step S1: Take 70 parts of the above hyperbranched epoxy resin, 8 parts of neopentyl glycol diglycidyl ether, 2.5 parts of organobentonite, 15 parts of modified mica powder, and 5 parts of iron oxide red, and prepare component A according to the method in Example 1.

[0071] Step S2: Select a modified alicyclic amine curing agent (amine value 240mg KOH / g) and mix component A and component B at a mass ratio of 5:1.

[0072] Comparative Example

[0073] Commercially available E-44 bisphenol A type epoxy resin was used as the main film-forming material, and the other fillers, additives and curing agents were the same as in Example 1.

[0074] Performance testing

[0075] The coatings of the present invention and the comparative example were applied to sandblasted Q235 steel plates and tested after curing for 7 days.

[0076]

[0077] Test results show that the coating of this invention is significantly superior to traditional epoxy coatings in terms of adhesion, toughness, and corrosion resistance.

Claims

1. An anti-corrosion coating, characterized in that, It is composed of component A and component B in a mass ratio of (4-6):1; Component A, by weight, comprises: 50-80 parts of hyperbranched epoxy resin; 5-15 parts of reactive diluent; 10-25 parts of sheet-like filler; Thixotropic agent 1-3 parts; 0-5 parts of pigment; Component B is a curing agent, and a modified alicyclic amine curing agent or a phenolic amine curing agent is selected. The hyperbranched epoxy resin has a number-average molecular weight of 2000-10000 g / mol, and its molecular structure is a hyperbranched polyester skeleton with triol as the core and glycidyl ether end capping, with a branching degree of not less than 0.

4.

2. The anti-corrosion coating according to claim 1, characterized in that, The active diluent is at least one of cashew phenol glycidyl ether or neopentyl glycol diglycidyl ether.

3. The anti-corrosion coating according to claim 1, characterized in that, The sheet-like filler is at least one of mica powder modified with a silane coupling agent, glass flakes, or aluminum hydroxide flakes, with a diameter-to-thickness ratio greater than 50.

4. A method for preparing a hyperbranched epoxy resin for use in the anti-corrosion coating of claim 1, characterized in that, Includes the following steps: S1. In the presence of a catalyst, a triol core and 2,2-dimethylolpropionic acid are subjected to a melt polycondensation reaction at 120-150°C for 4-8 hours to obtain hyperbranched polyester alcohol; S2. Dissolve the hyperbranched polyester alcohol obtained in step S1 in epichlorohydrin and carry out an epoxidation reaction at 60-80°C for 2-4 hours under alkaline conditions and in the presence of a phase transfer catalyst. S3. After the reaction is complete, the hyperbranched epoxy resin is obtained by washing with water and vacuum distillation.

5. The hyperbranched epoxy resin according to claim 4, characterized in that, The triol core component in step S1 may be selected from at least one of 1,1,1-trimethylolethane, 1,1,1-trimethylolpropane or glycerol, and the molar ratio with 2,2-dimethylolpropionic acid is 1:(6-21).

6. The hyperbranched epoxy resin according to claim 4, characterized in that, The catalyst in step S1 is at least one of p-toluenesulfonic acid, methanesulfonic acid, or tetraisopropyl titanate, and its addition amount is 0.5% to 1.5% of the total mass of the monomer.

7. The hyperbranched epoxy resin according to claim 4, characterized in that, In step S2, the molar ratio of epichlorohydrin to hydroxyl groups in hyperbranched polyester alcohol is controlled at (10-15):

1.

8. The hyperbranched epoxy resin according to claim 4, characterized in that, The phase transfer catalyst in step S2 is selected from at least one of tetrabutylammonium bromide, tetraethylammonium bromide or benzyltriethylammonium chloride, and its addition amount is 2% to 5% of the mass of the hyperbranched polyester alcohol.

9. The hyperbranched epoxy resin according to claim 4, characterized in that, In step S2, the molar ratio of sodium hydroxide to hydroxyl groups in hyperbranched polyester alcohol is (1.05-1.15):

1.

10. A method for preparing the anti-corrosion coating as described in claim 1, characterized in that, Includes the following steps: S1. Preparation of component A: Add the prescribed amount of hyperbranched epoxy resin and reactive diluent into a dispersion tank, stir at low speed until uniform, then add thixotropic agent, flake filler and pigment in sequence, and disperse at high speed (1000-1500 rpm) for 20-40 minutes; S2. Transfer the mixture to a sand mill and grind it to a fineness ≤30μm. Discharge and package as component A. S3. Mix component A and component B evenly according to the specified ratio, and allow to mature for 10-20 minutes before application.

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