Waterborne epoxy resin coating and preparation method thereof

Abstract

The invention belongs to the technical field of epoxy resin coatings, and particularly relates to a waterborne epoxy resin coating and a preparation method thereof. The waterborne epoxy resin coating is prepared from the following raw materials in percentage by mass: 5-70% of novolac epoxy resin F-516, 10-12% of hydroxyl-terminated polybutadiene, 5-7% of glycidyl methacrylate, 8-10% of a curing agent, 0.6-1.0% of a thermal initiator, 1-2% of a silane coupling agent, 0.3-0.5% of an auxiliary agent and the balance of deionized water, wherein the total percentage is 100%. Microencapsulated polyether amine in the water sample epoxy resin coating accurately releases polyether amine T-403 to realize controlled release of a curing agent, and by combining thermal triggering double-bond polymerization of dicumyl peroxide and interface stability of the silane coupling agent and synergistic effect of all the components, the coating is endowed with high adhesive force, high impact resistance, excellent salt spray corrosion resistance and low water vapor permeability; good application prospects are realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of epoxy resin coatings, and particularly relates to a waterborne epoxy resin coating and a preparation method thereof. Background Art

[0002] The waterborne epoxy resin coating is an environmentally friendly coating material based on a waterborne epoxy resin emulsion and formed by cross-linking reaction with a waterborne curing agent. Compared with traditional solvent-based epoxy coatings, its dispersant medium is water, supplemented with a small amount of co-solvents, defoamers, wetting agents and other additives to form a stable colloidal system. The waterborne epoxy resin coating forms a three-dimensional network structure through the cross-linking reaction of epoxy groups and curing agents, and can be applied to heavy anti-corrosion fields such as bridges, ships and petrochemical pipelines, and can also be used for floor coatings, building structure reinforcement, and high gloss for household appliances and automotive primers.

[0003] The prior art CN109021213B discloses a waterborne epoxy resin and a preparation method thereof, which carry out a ring-opening reaction of polyetheramine D230 with a monocyclic epoxide to generate an intermediate containing amino groups and ether bonds, and the intermediate undergoes a condensation reaction with epoxy resin to introduce a polyether chain segment to form an amphiphilic structure, and a waterborne epoxy resin is prepared. However, the ether bonds of the polyether chain segment are easily hydrolyzed under acidic conditions, and the salt spray corrosion resistance is insufficient, which easily leads to salt spray corrosion of the paint film in a chemical environment.

[0004] The information disclosed in this background art section is only intended to increase the understanding of the overall background of the present invention, and should not be regarded as an admission or any form of implication that this information constitutes the prior art already known to those of ordinary skill in the art. Summary of the Invention

[0005] The purpose of the present invention is to provide a waterborne epoxy resin coating and a preparation method thereof to solve the problems existing in the waterborne epoxy resin in the background art.

[0006] To achieve the above purpose, the present invention provides the following technical solutions:

[0007] A waterborne epoxy resin coating is prepared from the following raw materials by mass percentage: phenolic epoxy resin F-51 65-70%, hydroxyl-terminated polybutadiene 10-12%, glycidyl methacrylate 5-7%, curing agent 8-10%, thermal initiator 0.6-1.0%, silane coupling agent 1-2%, additive 0.3-0.5%, and deionized water is added to 100%.

[0008] Further, the curing agent is microencapsulated polyetheramine; the thermal initiator is diisopropylbenzene peroxide; the silane coupling agent is KH-560; the defoamer is BYK-024 defoamer.

[0009] Further, the preparation method of the microencapsulated polyetheramine is as follows:

[0010] a. React and mix polyetheramine T-403 with isophorone diisocyanate at a molar ratio of 1:1.2, and react at 60°C for 2 h under nitrogen protection to obtain a prepolymer;

[0011] b. Add the prepolymer to an aqueous solution of 2% Tween-80 with twice the mass, and emulsify at 5000 rpm for 5 min;

[0012] c. Dropwise add ethylenediamine with a mass of 4% of the prepolymer, react at 40°C for 4 h to form a polyurea wall material microcapsule, spray dry, and pass through a 10-μm sieve to obtain the microencapsulated polyetheramine.

[0013] The present invention also provides a preparation method of the waterborne epoxy resin coating, which includes the following steps:

[0014] S1. In a vacuum reactor, dehydrate hydroxyl-terminated polybutadiene at 110°C and -0.095 MPa for 2 h; cool down to 60°C, add glycidyl methacrylate, and pre-react at 60°C and 500 rpm for 1.5 h under nitrogen protection;

[0015] S2. Heat phenolic epoxy resin F-51 to 60°C in a stirring reactor, maintain stirring at 300 rpm for 30 min, then add it to the vacuum reactor in S1, and react at 60°C and 300 rpm for 1 h; add silane coupling agent KH-560, and react at 60°C and 500 rpm for 20 min;

[0016] S3. Mix the microencapsulated polyetheramine and dicumyl peroxide evenly and then add them to the reaction product of S2, react at 60°C and 400 rpm for 30 min; add BYK-024 defoamer, and carry out vacuum defoaming at 50°C and -0.08 MPa for 15 min;

[0017] S4. Add deionized water, stir at 300 rpm for 30 min, cool to room temperature, and filter under pressure of 0.3 MPa through a 200-mesh sieve to obtain the waterborne epoxy resin coating.

[0018] The present invention also provides a coating method of the waterborne epoxy resin coating. After coating the waterborne epoxy resin coating on a substrate, bake it at 120°C for 40 min for curing.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] In the waterborne epoxy resin coating of the present invention, the microencapsulated polyetheramine precisely releases polyetheramine T-403 to achieve the controlled release of the curing agent. Combining the thermal-triggered double-bond polymerization of dicumyl peroxide and the interfacial stabilization of silane coupling agent, the components act synergistically to endow the coating with high adhesion, high impact resistance, excellent salt spray corrosion resistance and low water vapor transmission rate, having good application prospects. Detailed implementation manners

[0021] The technical solutions of the present invention patent will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present invention.

[0022] 1. Influence of different raw material formulations on the performance of waterborne epoxy resin coatings

[0023] 1.1 Raw material formulations

[0024] See Table 1.

[0025] Table Raw material formulations of waterborne epoxy resin (mass percentage)

[0026]

[0027] 1.2 Microencapsulated polyetheramine

[0028] The preparation method of the microencapsulated polyetheramine in Table 1 includes the following steps:

[0029] a. React and mix polyetheramine T-403 (amine value 470) with isophorone diisocyanate at a molar ratio of 1:1.2, and react at 60 °C for 2 h under nitrogen protection to obtain a prepolymer;

[0030] b. Add the prepolymer to an aqueous solution of 2% Tween-80 with twice the mass, and emulsify at 5000 rpm for 5 min;

[0031] c. Dropwise add ethylenediamine with a mass of 4% of the prepolymer, react at 40 °C for 4 h to form a polyurea wall material microcapsule, spray dry, and pass through a 10 μm sieve to obtain the microencapsulated polyetheramine.

[0032] 1.3 Waterborne epoxy resin

[0033] The preparation method of the waterborne epoxy resin in Table 1 includes the following steps:

[0034] S1. In a vacuum reactor, dehydrate hydroxyl-terminated polybutadiene at 110 °C and -0.095 MPa for 2 h; cool down to 60 °C, add glycidyl methacrylate, and pre-react at 60 °C and 500 rpm for 1.5 h under nitrogen protection;

[0035] S2. Heat the phenolic epoxy resin F-51 in a stirring reactor to 60 °C, maintain stirring at 300 rpm for 30 min, then add it to the vacuum reactor in S1, and react at 60 °C and 300 rpm for 1 h; add the silane coupling agent KH-560 and react at 60 °C and 500 rpm for 20 min;

[0036] S3. Mix the microencapsulated polyetheramine and diisopropylbenzene peroxide evenly and then add them to the reaction product of S2, and react at 60 °C and 400 rpm for 30 min; add the BYK-024 defoaming agent and conduct vacuum defoaming at 50 °C and -0.08 MPa for 15 min;

[0037] S4. Add deionized water, stir at 300 rpm for 30 min, cool to room temperature, and filter under pressure of 0.3 MPa through a 200-mesh sieve to obtain the aqueous epoxy resin coating.

[0038] It should be noted that when the corresponding components are missing, the corresponding operations are removed.

[0039] 1.3 Measure the properties of the aqueous epoxy resin coating

[0040] The test items are shown in Table 2, and the test results are shown in Table 3.

[0041] Table 2 Test Items, Test Method Bases and Descriptions

[0042]

[0043] Table 3 Effects of Different Raw Material Formulations on the Properties of Epoxy Resin Coatings

[0044]

[0045] As can be seen from Table 3, in terms of adhesion, in the C4 coating, the microencapsulated polyetheramine precisely releases polyetheramine T-403 and combines with the silane coupling agent to enhance the interface, forming an interface layer, which can effectively improve the adhesion of the coating. In the C2 coating, the unencapsulated polyetheramine T-403 reacts in advance, resulting in uneven crosslinking and weak interface bonding. In addition, the C5 coating has no glycidyl methacrylate for compatibilization, resulting in phase separation between the hydroxyl-terminated polybutadiene and the phenolic epoxy resin F-51, and the adhesion drops sharply.

[0046] In terms of impact resistance, in the C4 coating, the toughening of hydroxyl-terminated polybutadiene, the crosslinking of glycidyl methacrylate, and the synergistic effect of stress dispersion by the silane coupling agent make the coating have high impact resistance; in the C6 coating, although there is crosslinking of glycidyl methacrylate, it lacks the flexible chain segments of hydroxyl-terminated polybutadiene, is significantly brittle, and has weak impact resistance; in the C5 coating, the absence of glycidyl methacrylate leads to phase separation, resulting in the worst impact resistance of the coating.

[0047] In terms of salt spray corrosion resistance, the double-network crosslinking (epoxy-amine + free radical) in C4 coating has high density, which can effectively improve the salt spray corrosion resistance of the coating. At the same time, the silane coupling agent can inhibit water vapor penetration and further improve the salt spray corrosion resistance of the coating; in C3 coating, dicumyl peroxide initiates double-bond crosslinking to strengthen the structure, but the lack of interface protection of the silane coupling agent results in a decrease in salt spray corrosion resistance; in C2 coating, the unencapsulated polyetheramine T-403 leads to uneven curing, resulting in poor salt spray corrosion resistance.

[0048] In terms of hardness and flexibility, the silane coupling agent in C4 coating enhances the interface bonding. The synergistic effect of hydroxyl-terminated polybutadiene and glycidyl methacrylate realizes the combination of rigidity and flexibility of the coating, endowing the coating with high hardness and flexibility; in C6 coating, the crosslinking of glycidyl methacrylate can improve the hardness, but the lack of hydroxyl-terminated polybutadiene results in poor flexibility of the coating; in C5 coating, the lack of crosslinking of glycidyl methacrylate leads to a decrease in hardness.

[0049] Overall, the microencapsulated polyetheramine in the C4 coating formula precisely releases polyetheramine T-403 to achieve controlled release of the curing agent. Combining the thermal-triggered double-bond polymerization of dicumyl peroxide and the interface stabilization of the silane coupling agent, the components work synergistically to achieve high adhesion, high impact resistance, excellent salt spray corrosion resistance, and low water vapor transmission rate. The comprehensive performance is significantly better than other formulations.

[0050] The foregoing description of the specific exemplary embodiments of the present invention is for the purposes of illustration and exemplification. These descriptions are not intended to limit the invention to the precise forms disclosed, and it is apparent that many changes and variations are possible in light of the above teachings. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the invention and its practical applications, so that those skilled in the art can implement and utilize the various different exemplary embodiments of the invention, as well as various different selections and changes. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A water-based epoxy resin coating, characterized in that: The invention is prepared from the following raw materials by mass percentage: 5-70% of phenolic epoxy resin F-516, 10-12% of terminal hydroxyl polybutadiene, 5-7% of glycidyl methacrylate, 8-10% of curing agent, 0.6-1.0% of thermal initiator, 1-2% of silane coupling agent, 0.3-0.5% of auxiliary agent, and deionized water is added to 100%.

2. The waterborne epoxy resin coating according to claim 1, characterized in that: The curing agent is microencapsulated polyetheramine; the thermal initiator is dicumyl peroxide; the silane coupling agent is KH-560; and the defoaming agent is BYK-024 defoaming agent.

3. The waterborne epoxy resin coating according to claim 2, characterized in that: The preparation method of the microencapsulated polyetheramine is as follows: a. Mix polyetheramine T-403 and isophorone diisocyanate in a molar ratio of 1:1.2, and react at 60°C for 2 hours under nitrogen protection to obtain a prepolymer; b. Add the prepolymer to 2 times the mass of 2% Tween-80 aqueous solution and emulsify at 5000rpm for 5min; c. 4% by weight of ethylenediamine prepolymer was added dropwise, and the mixture was reacted at 40°C for 4 hours to form polyurea wall microcapsules, which were spray dried and passed through a 10 μm sieve to obtain the microencapsulated polyetheramine.

4. A method for preparing the waterborne epoxy resin coating according to claim 2, characterized in that: The following steps are involved: S1. Dehydrate the hydroxy-terminated polybutadiene in a vacuum reactor at 110°C and -0.095MPa for 2h; cool to 60°C, add glycidyl methacrylate, and pre-react at 60°C and 500rpm for 1.5h under nitrogen protection; S2. Heat the phenolic epoxy resin F-51 to 60°C in a stirred reactor, maintain stirring at 300 rpm for 30 min, then add it to the vacuum reactor in S1, react at 60°C, 300 rpm for 1 h; add the silane coupling agent KH-560, react at 60°C, 500 rpm for 20 min; S3. The microencapsulated polyetheramine and dicumyl peroxide were mixed and then added to the reaction product of S2, and the reaction was carried out at 60°C and 400rpm for 30min; BYK-024 defoamer was added, and vacuum defoaming was carried out at 50°C and -0.08MPa for 15min; S4. Add deionized water, stir at 300 rpm for 30 min, cool to room temperature, and filter under pressure at 0.3 MPa through a 200-mesh sieve to obtain the water-based epoxy resin coating.

5. A coating method of the waterborne epoxy resin coating according to claim 2, characterized in that: After the waterborne epoxy resin coating is applied to the substrate, it is baked at 120° C. for 40 minutes to be cured.

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