Corrosion-resistant epoxy resin coating and preparation method thereof

Abstract

The invention belongs to the technical field of epoxy resin coatings, and particularly relates to a corrosion-resistant epoxy resin coating and a preparation method thereof. The invention relates to a corrosion-resistant epoxy resin coating which is prepared from the following raw materials in percentage by mass: 30-38% of a base material, 20-24% of a compound curing agent, 20-23% of a solvent, 8-10% of a compound filler, 1-3% of a functional aid and the balance of deionized water, wherein the base material is itaconic anhydride modified bisphenol A epoxy resin; the compound curing agent is composed of methylhexahydrophthalic anhydride and cardanol modified amine; the solvent is propylene glycol methyl ether acetate; the compound filler is composed of ferrophosphorus powder and talcum powder. The raw materials are matched with one another, so that the prepared coating has excellent properties in the aspects of adhesive force, impact resistance, salt spray corrosion resistance, humidity and heat resistance, chemical resistance and the like.

Description

Technical Field

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

[0002] Epoxy resin coatings are high-performance coatings that use epoxy resin as the main film-forming substance and form a three-dimensional network structure through cross-linking reactions with curing agents. Their main components include epoxy resin base materials, curing agents, solvents, fillers, and functional additives, etc. The epoxy resin molecule contains active groups such as epoxy groups and hydroxyl groups, which endow the coating with adhesion, mechanical strength, and chemical corrosion resistance. Due to its outstanding comprehensive performance, epoxy resin coatings are widely used in the protection of heavily corroded environments such as ships, bridges, chemical equipment, and underground pipelines.

[0003] Traditional epoxy resin coatings are usually based on bisphenol A epoxy resin and achieve room-temperature or high-temperature curing through amine or anhydride curing agents. Then, their solvents mostly use highly volatile organic compounds (VOCs) such as toluene and xylene, which pose serious hazards to the environment and human health; the curing agents mainly rely on petrochemical raw materials, which do not meet the requirements of sustainable development; in addition, the physical barrier ability of conventional fillers (such as silica and talcum powder) to corrosive media is limited, and long-term exposure to acid-base and salt spray environments is likely to cause coating failure.

[0004] In recent years, in view of the above problems, some improvement schemes have been proposed in the prior art:

[0005] a. Using water as a dispersant to reduce VOC emissions, but the aqueous system has problems such as slow curing speed and poor water resistance, and it is difficult to meet the requirements of heavily corroded scenarios.

[0006] b. Adding nano-fillers such as graphene and carbon nanotubes to improve the shielding performance, but the nano-materials are difficult to disperse and have a high cost, which will increase the production cost of the coating.

[0007] c. Using bio-based curing agents such as cardanol-modified amines, but a single curing agent is difficult to balance the room-temperature curing speed and high-temperature resistance performance.

[0008] Based on the above problems, it is urgent to develop a new type of corrosion-resistant epoxy resin coating. Summary of the Invention

[0009] The purpose of the present invention is to provide a corrosion-resistant epoxy resin coating and a preparation method thereof to solve the problems existing in the existing epoxy resin coatings in the background art.

[0010] To achieve the above purpose, the present invention provides the following technical solutions:

[0011] A corrosion-resistant epoxy resin coating, calculated by mass percentage, is prepared from the following raw materials: 30-38% of a base material, 20-24% of a compound curing agent, 20-23% of a solvent, 8-10% of a compound filler, 1-3% of a functional additive, and deionized water is added to make up 100%;

[0012] Among them, the base material is itaconic anhydride-modified bisphenol A epoxy resin;

[0013] The compound curing agent is composed of methylhexahydrophthalic anhydride and cardanol-modified amine;

[0014] The solvent is propylene glycol methyl ether acetate;

[0015] The compound filler is composed of ferrophosphorus powder and talc powder.

[0016] Furthermore, the preparation method of the itaconic anhydride-modified bisphenol A epoxy resin includes the following steps:

[0017] a. After purging the air in the reaction kettle with nitrogen 3 times, set the stirring speed at 200 rpm, put the bisphenol A epoxy resin into the reaction kettle, and heat it up to 70 °C;

[0018] b. Add itaconic anhydride, keep the temperature at 70 °C, and stir at 200 rpm for 30 min; add the catalyst 1-butyl-3-methylimidazole acetate, and stir at 200 rpm for 10 min;

[0019] c. Heat up to 80 °C, start the condensing reflux, and continuously purge with nitrogen for protection. After reacting for 3 h, cool down to 50 °C, stop stirring, and let it stand for 15 min. The mixture forms an upper organic phase and a lower aqueous phase;

[0020] d. Add deionized water with a volume of 1 / 3 of the organic phase volume to the reaction kettle, stir at 200 rpm for 10 min to fully dissolve the catalyst in water, let it stand for 20 min, drain the lower aqueous phase containing the catalyst, repeat 3 times, and then distill under reduced pressure to remove the water in the aqueous phase and recover the catalyst;

[0021] e. Dehydrate the upper organic phase at 80 °C and -0.095 MPa until the water content is lower than 0.1%, and then the itaconic anhydride-modified bisphenol A epoxy resin is obtained.

[0022] Furthermore, the mass ratio of the methylhexahydrophthalic anhydride to the cardanol-modified amine is 5:3.

[0023] Furthermore, the mass ratio of the ferrophosphorus powder to the talc powder is 7:3.

[0024] Further, the functional additives include a leveling agent, an antifoaming agent, and a silane coupling agent; among them, the mass of the leveling agent accounts for 0.5% of the total mass of the raw materials of the corrosion-resistant epoxy resin coating; the mass of the antifoaming agent accounts for 0.3% of the total mass of the raw materials of the corrosion-resistant epoxy resin coating; the mass of the silane coupling agent accounts for 1.5% of the total mass of the raw materials of the corrosion-resistant epoxy resin coating.

[0025] The present invention also provides a preparation method of the corrosion-resistant epoxy resin coating, including the following steps:

[0026] S1. Add itaconic anhydride-modified bisphenol A epoxy resin and a solvent to a dispersion tank, and stir at 800 rpm for 15 min;

[0027] S2. Sequentially add ferrophosphorus powder and talc powder, increase the rotation speed to 2000 rpm, and disperse for 40 min; add a silane coupling agent, and disperse at 2000 rpm for 20 min;

[0028] S3. Reduce the rotation speed to 1000 rpm, add a leveling agent, an antifoaming agent, and deionized water, and stir for 10 min;

[0029] S4. Transfer the material to a sand mill for grinding and pass through a 30-μm sieve, and then perform vacuum defoaming at 25°C and -0.08 MPa for 30 min;

[0030] S5. Add methylhexahydrophthalic anhydride and cashew phenol-modified amine, stir at 600 rpm for 20 min, and let stand for 5 - 10 min to obtain the corrosion-resistant epoxy resin coating.

[0031] The present invention also provides a coating method of the corrosion-resistant epoxy resin coating, specifically: Treat the surface of the metal substrate to be clean and dry, and spray or roll-coat the corrosion-resistant epoxy resin coating to a wet film thickness of 100 - 120 μm.

[0032] The present invention also provides a curing method of the corrosion-resistant epoxy resin coating, specifically: After curing at room temperature for 24 h, cure at 80°C for 2 h.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] The itaconic anhydride-modified bisphenol A epoxy resin of the present invention can significantly improve the corrosion resistance, adhesion and chemical resistance of coatings; methylhexahydrophthalic anhydride forms an ester bond network at high temperatures and has excellent heat resistance, while the cardanol-modified amine cures at room temperature to accelerate curing and improve toughness. When they cooperate with each other, the impact resistance and hardness of the coatings can be improved; the phosphorus iron powder releases iron ions and phosphate ions to inhibit the electrochemical corrosion of the substrate, and the lamellar arrangement structure of talcum powder can extend the diffusion path of the corrosive medium. When they cooperate with each other, the salt spray corrosion resistance of the coatings can be significantly improved. The mutual cooperation of each raw material enables the prepared coatings to have excellent performance in terms of adhesion, impact resistance, salt spray corrosion resistance, damp heat resistance and chemical resistance. Detailed implementation manners

[0035] 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 them. All other embodiments obtained by those skilled in the art within the scope of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0036] In the following examples, the bisphenol A epoxy resin is of the EPON TM 828 type; the cardanol-modified amine is of the talcum powder is of the HAR T84 type, and the rest of the reagents are commercially available.

[0037] 1. Influence of different raw material formulations on the performance of epoxy resin coatings

[0038] 1.1 Raw material formulation of epoxy resin coatings

[0039] See Table 1.

[0040] Table 1 Raw material formulation of epoxy resin coatings (mass percentage)

[0041]

[0042] Note in Table 1: The modified epoxy resin is itaconic anhydride-modified bisphenol A epoxy resin; the unmodified epoxy resin is bisphenol A epoxy resin.

[0043] 1.2 Itaconic anhydride-modified bisphenol A epoxy resin

[0044] The preparation method of the itaconic anhydride-modified bisphenol A epoxy resin in Table 1 includes the following steps:

[0045] a. After purging the air in the reaction kettle with nitrogen three times, set the stirring speed to 200 rpm, add 76 kg of bisphenol A epoxy resin to the reaction kettle, and heat it up to 70 °C;

[0046] b. Add 24 kg of itaconic anhydride, maintain the temperature at 70 °C, stir at 200 rpm for 30 min; add 1.2 kg of catalyst 1-butyl-3-methylimidazolium acetate, stir at 200 rpm for 10 min;

[0047] c. Raise the temperature to 80 °C, start the condensation reflux, and continuously pass nitrogen for protection. After reacting for 3 h, cool down to 50 °C, stop stirring, let it stand for 15 min, and the mixture forms an upper organic phase and a lower aqueous phase;

[0048] d. Add deionized water with a volume of 1 / 3 of the organic phase to the reaction kettle, stir at 200 rpm for 10 min to fully dissolve the catalyst in water, let it stand for 20 min, drain the lower aqueous phase containing the catalyst, repeat 3 times, and then remove the moisture in the aqueous phase by vacuum distillation to recover the catalyst;

[0049] e. Dehydrate the upper organic phase at 80 °C and -0.095 MPa until the moisture content is lower than 0.1%, and then the itaconic anhydride-modified bisphenol A epoxy resin is obtained.

[0050] 1.3 Epoxy resin coating

[0051] The preparation method of the epoxy resin coating in Table 1 includes the following steps:

[0052] S1. Add the itaconic anhydride-modified bisphenol A epoxy resin and propylene glycol monomethyl ether acetate to the dispersion tank, and stir at 800 rpm for 15 min;

[0053] S2. Add iron phosphate powder and talc powder in sequence, increase the rotation speed to 2000 rpm, and disperse for 40 min; add silane coupling agent KH-550, and disperse at 2000 rpm for 20 min;

[0054] S3. Reduce the rotation speed to 1000 rpm, add BYK-358 leveling agent, BYK-077 defoaming agent, and deionized water, and stir for 10 min;

[0055] S4. Transfer the material to a sand mill for grinding and pass through a 30 μm sieve, and then carry out vacuum defoaming at 25 °C and -0.08 MPa for 30 min;

[0056] S5. Add methylhexahydrophthalic anhydride and cashew phenol-modified amine, stir at 600 rpm for 20 min, and let it stand for 5 - 10 min to obtain the corrosion-resistant epoxy resin coating.

[0057] 1.4 Coating and curing

[0058] The coating method is specifically as follows: Treat the surface of the metal substrate until it is clean and dry, spray or roll-coat the corrosion-resistant epoxy resin coating to a wet film thickness of 100 - 120 μm, and the surface dries in 4 h.

[0059] The curing method is specifically as follows: cure at room temperature of 25°C for 24 hours, and then cure at 80°C for 2 hours.

[0060] 1.5 Measure the properties of the epoxy resin coating

[0061] The test items are shown in Table 2, and the test results are shown in Table 3.

[0062] Table 2 Test Items, Test Method Bases and Descriptions

[0063]

[0064]

[0065] Table 3 Influence of Different Raw Material Formulations on the Properties of Epoxy Resin Coatings

[0066]

[0067] As can be seen from Table 3, overall, the coatings prepared from C7 raw materials have excellent properties in terms of adhesion, impact resistance, salt spray corrosion resistance, damp heat resistance, and chemical resistance. It shows that itaconic anhydride-modified bisphenol A epoxy resin can significantly improve corrosion resistance, adhesion, and chemical resistance; methylhexahydrophthalic anhydride forms an ester bond network at high temperatures and has excellent heat resistance, while cardanol-modified amine accelerates curing at room temperature and improves toughness. Their cooperation can improve the impact resistance and hardness of the coating; phosphorus iron powder releases iron ions and phosphate ions to inhibit the electrochemical corrosion of the substrate, and the lamellar arrangement structure of talc powder can extend the diffusion path of the corrosion medium. Their cooperation can significantly improve the salt spray corrosion resistance of the coating.

[0068] The foregoing description of specific exemplary embodiments of the present invention is for purposes of illustration and exemplification. These descriptions are not intended to limit the present invention to the precise forms disclosed, and obviously, 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 present invention and its practical applications, so that those skilled in the art can implement and utilize various different exemplary embodiments of the present invention, as well as various different selections and changes. The scope of the present invention is intended to be defined by the claims and their equivalents.

Claims

1. A corrosion-resistant epoxy resin coating, characterized in that: The corrosion-resistant epoxy resin coating is prepared from the following raw materials in terms of mass percentage: 30-38% base material, 20-24% compound curing agent, 20-23% solvent, 8-10% compound filler, 1-3% functional additive, and deionized water supplemented to 100%; Wherein, the base material is itaconic anhydride modified bisphenol A type epoxy resin; The composite curing agent is composed of methyl hexahydrophthalic anhydride and cardanol modified amine; The solvent is propylene glycol methyl ether acetate; The composite filler consists of ferrophosphorus powder and talcum powder.

2. The corrosion-resistant epoxy resin coating according to claim 1, characterized in that: The preparation method of the itaconic anhydride modified bisphenol A type epoxy resin comprises the following steps: a. After replacing the air with nitrogen in the reactor three times, set the stirring speed to 200 rpm, and heat the bisphenol A epoxy resin reactor to 70 ° C; b. Add itaconic anhydride, maintain the temperature at 70°C, and stir at 200 rpm for 30 min; add catalyst 1-butyl-3-methylimidazolium acetate, and stir at 200 rpm for 10 min; c. Raise the temperature to 80°C, start condensation reflux, and continue nitrogen protection. After reacting for 3 hours, cool to 50°C, stop stirring, and let stand for 15 minutes. The mixture forms an upper organic phase and a lower aqueous phase; d. Add 1 / 3 of the volume of the organic phase to the reactor with deionized water, stir at 200 rpm for 10 min to fully dissolve the catalyst in water, let stand for 20 min, discharge the lower aqueous phase containing the catalyst, repeat 3 times, and then remove the water in the aqueous phase by vacuum distillation to recover the catalyst; e. The upper organic phase was dehydrated at 80°C and -0.095 MPa to a moisture content of less than 0.1%, thereby obtaining itaconic anhydride-modified bisphenol A epoxy resin.

3. The corrosion-resistant epoxy resin coating according to claim 1, characterized in that: The mass ratio of the methyl hexahydrophthalic anhydride to the cardanol modified amine is 5:

3.

4. The corrosion-resistant epoxy resin coating according to claim 1, characterized in that: The mass ratio of the ferrophosphorus powder to the talcum powder is 7:

3.

5. The corrosion-resistant epoxy resin coating according to claim 1, characterized in that: The functional additives include a leveling agent, a defoaming agent and a silane coupling agent; wherein the mass of the leveling agent accounts for 0.5% of the total mass of the corrosion-resistant epoxy resin coating raw material; The mass of the defoamer accounts for 0.3% of the total mass of the corrosion-resistant epoxy resin coating raw material; The mass of the silane coupling agent accounts for 1.5% of the total mass of the corrosion-resistant epoxy resin coating raw material.

6. A method for preparing the corrosion-resistant epoxy resin coating according to claim 5, characterized in that: The following steps are involved: S1. The itaconic anhydride-modified bisphenol A epoxy resin and the solvent were added to a dispersion tank and stirred at 800 rpm for 15 min; S2. Add ferrophosphorus powder and talcum powder in turn, increase the speed to 2000rpm, and disperse for 40min; add silane coupling agent and disperse at 2000rpm for 20min; S3. Reduce the speed to 1000 rpm, add leveling agent, defoamer, deionized water, and stir for 10 minutes; S4. The material was transferred to a sand mill and ground through a 30 μm sieve, and then vacuum degassed at 25°C and -0.08 MPa for 30 min; S5. Add methyl hexahydrophthalic anhydride and cardanol modified amine, stir at 600 rpm for 20 min, and let stand for 5-10 min to obtain the corrosion-resistant epoxy resin coating.

7. A coating method of the corrosion-resistant epoxy resin coating according to any one of claims 1 to 5, characterized in that: Specifically, the surface of the metal substrate is treated to be clean and dry, and the corrosion-resistant epoxy resin coating is sprayed or rolled to a wet film thickness of 100-120 μm.

8. A method for curing the corrosion-resistant epoxy resin coating according to any one of claims 1 to 5, characterized in that: Specifically: after curing at room temperature for 24 hours, cure at 80℃ for 2 hours.

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