Anticorrosive epoxy resin coating for steel structure in marine environment and preparation method of anticorrosive epoxy resin coating

Abstract

The invention discloses an anticorrosive epoxy resin coating for a steel structure in a marine environment and a preparation method thereof, and belongs to the field of coating preparation. The epoxy resin coating is prepared by preparing the modified epoxy resin and filling the functional filler for modification, and p-hydroxybenzoic acid, pyrrolidone and methyl methacrylate are added for copolymerization in an epoxy resin monomer polymerization stage, so that the ultraviolet resistance and thermal stability of the coating are enhanced; titanium dioxide is subjected to surface modification by using a supramolecular compound dibenzo 21-crown-7 and polypropylene glycol to prepare a functional filler, so that the flexibility and ductility of the epoxy resin are improved, and the ultraviolet resistance of a paint film is improved. The epoxy resin coating prepared by the method disclosed by the invention not only has excellent adhesion and corrosion resistance, but also has excellent ultraviolet resistance, high temperature resistance and good flexibility, and is particularly suitable for corrosion protection of a steel structure in a marine environment.

Description

Technical Field

[0001] The present invention relates to a novel epoxy resin coating and its preparation method, belonging to the field of coating preparation. Specifically, the present invention relates to an anti-corrosion coating with excellent ultraviolet resistance, high-temperature performance, and good flexibility, which is particularly suitable for the anti-corrosion protection of steel structures under extreme weather conditions in the marine environment. Background Art

[0002] Epoxy resin coatings are widely used in the anti-corrosion field of marine steel structures due to their excellent corrosion resistance, good adhesion, and outstanding mechanical properties. They can effectively isolate moisture, salts, and harmful substances in the air, prevent steel from undergoing oxidation corrosion, and extend the service life of the structure. In the marine environment, epoxy resin coatings are usually used for the anti-corrosion primer and intermediate coat of steel structures. Their strong adhesion and chemical resistance make them an ideal protective material for facilities such as offshore oil platforms, submarine pipelines, wind power platforms, and marine bridges. Despite the significant advantages of epoxy resin coatings in anti-corrosion, they still face some problems that need to be urgently solved. First, the long-term exposure of epoxy resin coatings to ultraviolet rays, oxygen, and humidity will cause coating aging, resulting in phenomena such as fading, cracking, and peeling. Especially in an environment with strong ultraviolet rays and sea breeze erosion, the weather resistance is poor, affecting the durability and protective effect of the coating. Second, due to the relatively high hardness of the epoxy resin coating and the lack of sufficient flexibility, when subjected to impact or structural deformation, the coating is prone to cracking or peeling.

[0003] Patent CN115007428A discloses an anti-corrosion method for the support structure of a wind turbine in the marine environment. The method includes degreasing and derusting the support structure, and then spraying a conductive polyaniline composite primer, an epoxy mica iron intermediate coat, and a top coat in sequence, and pasting an anti-corrosion tape outside the top coat. By using a conductive polyaniline composite primer to replace the traditional zinc-rich primer, the zinc content in the coating is reduced, avoiding problems such as reduced adhesion and decreased impact resistance strength caused by excessive zinc, while achieving the anti-corrosion effect. However, the multi-layer coating process makes the actual construction process relatively complex, and at the same time, the influence of extreme marine climate on the coating and the flexibility of the coating are not fully considered.

[0004] Patent CN118562380A discloses an anti-corrosion coating for outdoor steel structures and its preparation method, which includes component A and component B. Component A includes aqueous polyurethane emulsion, dispersant, preservative, etc.; Component B includes composite modified resin emulsion, polyvinyl acetate, and boron nitride nanosheet-graphene composite material. By mixing nitrile rubber, vinyl polyester resin, and n-propanol, dropping hydrochloric acid for reaction, adding a capping agent and copolymer for capping, and finally adding an initiator and carbon nanotubes, distilling off the solvent and emulsifying, a composite modified resin emulsion is obtained. This method effectively solves the problems of flammability, high VOC, and decreased adhesion. However, this coating may not be suitable for extreme weather conditions such as high ultraviolet rays and high temperatures in the marine environment.

[0005] There are various erosion media in the marine environment, resulting in durability problems such as rust, chloride ion erosion, and sulfate corrosion of steel structures. However, there is still a lack of coatings that can exhibit excellent weather resistance under extreme conditions in the ocean. In particular, existing coatings still have obvious deficiencies in terms of ultraviolet resistance and flexibility. Summary of the Invention

[0006] The purpose of the present invention is to provide an anti-corrosion epoxy resin coating for steel structures in the marine environment and its preparation method, aiming at the problems of poor weather resistance and insufficient coating flexibility that occur when existing epoxy resin coatings for marine steel structures are used. This coating has excellent ultraviolet and high-temperature resistance and good flexibility, and is particularly suitable for the anti-corrosion protection of steel structures under extreme weather conditions in the marine environment.

[0007] The technical solution adopted by the present invention is as follows: A preparation method of an anti-corrosion epoxy resin coating for steel structures in the marine environment includes the following steps: (1) Preparation of modified epoxy resin: ① By weight, take 25 - 30 parts of bisphenol a, 65 - 70 parts of epichlorohydrin, 1 - 3 parts of p-hydroxybenzoic acid, and 1 - 3 parts of pyrrolidone and place them in a reaction kettle. Heat to 150 - 160 °C. After the reactants melt, add 0.2 parts of dimethylaniline, stir and react for 5 - 6 h, add an appropriate amount of sulfuric acid to neutralize dimethylaniline, and cool to room temperature to obtain modified epoxy resin a; ② By weight, take 25 - 30 parts of bisphenol a, 65 - 70 parts of epichlorohydrin, 5 - 8 parts of methyl methacrylate, and place them in a reaction kettle. Heat to 130 - 150 °C. After the reactants melt, add 0.2 parts of benzoyl peroxide, stir for 3 - 4 h, add 0.1 - 0.2 parts of hydroquinone for polymerization inhibition, and cool to room temperature to obtain modified epoxy resin b; ③ Mix and stir modified epoxy resin a and modified epoxy resin b evenly to obtain the modified epoxy resin; (2) Preparation of functional fillers: By weight parts, take 95 - 100 parts of titanium dioxide with a particle size between 100 - 150 nm, place it in a high - speed stirring kettle, heat it to 80 - 90 °C, and then successively add 5 - 6 parts of dibenzo - 21 - crown - 7 and 2 - 3 parts of polypropylene glycol. After high - speed stirring for 30 - 40 min, the functional filler is obtained. (3) By weight parts, take 55 - 60 parts of modified epoxy resin; 18 - 20 parts of curing agent; 15 - 17 parts of solvent; 2 - 3 parts of leveling agent; 3 - 5 parts of 200 - mesh butyl rubber particles; 15 - 18 parts of functional filler. Use a double - planetary mixer to mix and stir all the materials for 1 h to obtain the coating.

[0008] Further, in the preparation method of the epoxy resin coating for steel structure anti - corrosion in the marine environment, in step (2), for the high - speed stirring, the rotation speed is 300 - 400 r / min.

[0009] Further, in the preparation method of the epoxy resin coating for steel structure anti - corrosion in the marine environment, in step (3), the curing agent selected is one or more of triethylenetetramine, diaminodiphenylmethane or 4,4'-diaminodiphenylmethane.

[0010] Further, in step (3), the solvent selected is one or more of xylene, dimethyl sulfoxide or toluene.

[0011] Further, in step (3), the leveling agent selected is one or more of trifluorochlorosilane, polydimethylsiloxane or polyacrylate.

[0012] The present invention also provides an epoxy resin coating prepared by using the above - mentioned preparation method of the epoxy resin coating for steel structure anti - corrosion in the marine environment. This epoxy resin coating can be used for the anti - corrosion protection of steel structures in the marine environment.

[0013] The present invention modifies the epoxy resin coating through the copolymerization modification of anti - ultraviolet heat - resistant monomers and filling with functional fillers, and then prepares an epoxy resin coating with excellent adhesion and anti - corrosion performance, having excellent ultraviolet resistance, high - temperature resistance and good flexibility, and being suitable for the anti - corrosion protection of steel structures in the marine environment. The modification principle of the present invention is as follows: 1. Copolymerization modification of anti - ultraviolet heat - resistant monomers. In the polymerization stage of epoxy resin monomers, add p - hydroxybenzoic acid, pyrrolidone and methyl methacrylate for copolymerization. p - Hydroxybenzoic acid and pyrrolidone respectively have a benzene ring and a five - membered nitrogen - containing heterocycle. This ring system can effectively absorb ultraviolet radiation, especially in the ultraviolet C (UVC) and ultraviolet B (UVB) bands, so as to enhance the ultraviolet aging resistance of the coating. After copolymerization with methyl methacrylate, the molecular cross - linking degree increases, which makes the modified molecular chain have higher thermal stability.

[0014] 2. Fill with functional fillers. Use the supramolecular compound dibenzo-21-crown-7 and polypropylene glycol to modify the surface of titanium dioxide with a particle size between 100 and 150 nm. Dibenzo-21-crown-7 can form a coordination complex in the epoxy resin, reducing the crosslinking degree between resin segments, thereby improving the flexibility and ductility of the epoxy resin. Polypropylene glycol has a long chain segment and a similar structure to the epoxy resin, increasing the flexibility of the molecular chain and impact resistance, and solving the problem of filler dispersion in the epoxy resin. Titanium dioxide can absorb ultraviolet light, further improving the ultraviolet resistance of the paint film.

[0015] The beneficial effects of the present invention are as follows: The present invention provides an anti-corrosion epoxy resin coating for steel structures in a marine environment and a preparation method thereof. The present invention modifies and prepares the epoxy resin coating through copolymerization modification of anti-ultraviolet heat-resistant monomers and filling with functional fillers, effectively improving the thermal stability and weather resistance of the prepared epoxy resin coating, and improving the ultraviolet resistance and flexibility of the paint film.

[0016] The epoxy resin coating prepared by the present invention adopts a single-layer coating process, which is simple to construct. Moreover, the coating not only has excellent adhesion and anti-corrosion performance, but also has excellent ultraviolet resistance, high temperature resistance and good flexibility. Therefore, it is particularly suitable for the anti-corrosion protection of steel structures under extreme weather conditions in a marine environment. Specific embodiments

[0017] All the following examples and comparative examples are formulated into coatings according to the coating formula in Table 1 below.

[0018] Example 1

[0019] A preparation method of an anti-corrosion epoxy resin coating for steel structures in a marine environment includes the following steps: (1) Preparation of modified epoxy resin: ① Take 25 parts of bisphenol a, 65 parts of epichlorohydrin, 2 parts of p-hydroxybenzoic acid, and 1 part of pyrrolidone by weight and place them in a reaction kettle. Heat to 155 °C. After the reactants melt, add 0.2 parts of dimethylaniline and react under stirring for 5 h. Add an appropriate amount of sulfuric acid to neutralize dimethylaniline, and cool to room temperature to obtain modified epoxy resin a. ② Take 30 parts of bisphenol a, 70 parts of epichlorohydrin, and 6 parts of methyl methacrylate by weight and place them in a reaction kettle. Heat to 140 °C. After the reactants melt, add 0.2 parts of benzoyl peroxide and stir for 4 h. Add 0.1 part of hydroquinone for polymerization inhibition, and cool to room temperature to obtain modified epoxy resin b. ③ Mix and stir modified epoxy resins a and b evenly to obtain the modified epoxy resin of Example 1.

[0020] (2) Preparation of functional filler: By weight, take 95 parts of titanium dioxide with a particle size between 100 and 150 nm, place it in a high-speed stirring kettle, heat it to 90 °C, and then add 6 parts of dibenzo-21-crown-7 and 3 parts of polypropylene glycol in sequence. After high-speed stirring (350 r / min) for 30 min, the filler of Example 1 is obtained.

[0021] (3) According to the coating formula in Table 1, add the modified epoxy resin, filler and other raw material components obtained in steps (1) and (2) respectively, and use a double planetary mixer to stir all the materials for 1 h to obtain the sample coating of Example 1. Example 2

[0022] A preparation method of an epoxy resin coating for anti-corrosion of steel structures in a marine environment includes the following steps: (1) Preparation of modified epoxy resin: ① By weight, take 28 parts of bisphenol A, 68 parts of epichlorohydrin, 1 part of p-hydroxybenzoic acid, and 3 parts of pyrrolidone and place them in a reaction kettle. Heat it to 150 °C. After the reactants melt, add 0.2 part of dimethylaniline, react under stirring for 5.5 h, add an appropriate amount of sulfuric acid to neutralize dimethylaniline, and cool to room temperature to obtain modified epoxy resin a. ② By weight, take 28 parts of bisphenol A, 68 parts of epichlorohydrin, and 7 parts of methyl methacrylate and place them in a reaction kettle. Heat it to 135 °C. After the reactants melt, add 0.2 part of benzoyl peroxide, stir for 4 h, add 0.2 part of hydroquinone for polymerization inhibition, and cool to room temperature to obtain modified epoxy resin b. ③ Mix and stir modified epoxy resins a and b evenly to obtain the modified epoxy resin of Example 2.

[0023] (2) Preparation of functional filler: By weight, take 100 parts of titanium dioxide with a particle size between 100 and 150 nm, place it in a high-speed stirring kettle, heat it to 90 °C, and then add 5 parts of dibenzo-21-crown-7 and 2 parts of polypropylene glycol in sequence. After high-speed stirring (330 r / min) for 40 min, the filler of Example 2 is obtained.

[0024] (3) According to the coating formula in Table 1, add the modified epoxy resin, filler and other raw material components obtained in steps (1) and (2) respectively, and use a double planetary mixer to stir all the materials for 1 h to obtain the sample coating of Example 2.

[0025] Comparative Example 1 (1) By weight, take 25 parts of bisphenol A and 65 parts of epichlorohydrin and place them in a reaction kettle. Heat it to 150 °C. After the reactants melt, add 0.2 part of dimethylaniline, react under stirring for 5 h, add an appropriate amount of sulfuric acid to neutralize dimethylaniline, and cool to room temperature to obtain epoxy resin.

[0026] (2) Take 95 parts by weight of titanium dioxide with a particle size between 100 and 150 nm, place it in a high-speed stirring kettle, heat it to 90 °C, and then stir at a high speed (360 r / min) for 30 min to obtain the filler of Comparative Example 1.

[0027] (3) According to the coating formula in Table 1, add the epoxy resin, filler and other raw material components obtained in steps (1) and (2) respectively, and use a double planetary mixer to stir all the materials for 1 h to obtain the sample coating of Comparative Example 1.

[0028] Comparative Example 2 (1) Take 28 parts by weight of bisphenol a and 68 parts by weight of epichlorohydrin, heat it to 150 °C, wait for the reactants to melt, add 0.2 parts of dimethylaniline, react for 5.5 h under stirring, add an appropriate amount of sulfuric acid to neutralize dimethylaniline, and cool to room temperature to obtain the epoxy resin.

[0029] (2) Take 98 parts by weight of titanium dioxide with a particle size between 100 and 150 nm, place it in a high-speed stirring kettle, heat it to 90 °C, and then add 6 parts of dibenzo-21-crown-7 and 3 parts of polypropylene glycol in sequence, and stir at a high speed (350 r / min) for 30 min to obtain the filler of Comparative Example 2.

[0030] (3) According to the coating formula in Table 1, add the epoxy resin, filler and other raw material components obtained in steps (1) and (2) respectively, and use a double planetary mixer to stir all the materials for 1 h to obtain the sample coating of Comparative Example 2.

[0031] Comparative Example 3 (1) Take 29 parts by weight of bisphenol a, 67 parts by weight of epichlorohydrin, 1 part of p-hydroxybenzoic acid, and 3 parts of pyrrolidone and place them in a reaction kettle, heat it to 150 °C, wait for the reactants to melt, add 0.2 parts of dimethylaniline, react for 5.5 h under stirring, add an appropriate amount of sulfuric acid to neutralize dimethylaniline, and cool to room temperature to obtain the modified epoxy resin a3. Take 26 parts by weight of bisphenol a, 69 parts by weight of epichlorohydrin, and 7 parts of methacrylate and place them in a reaction kettle, heat it to 135 °C, wait for the reactants to melt, add 0.2 parts of benzoyl peroxide, stir for 4 h, add 0.1 part of hydroquinone for polymerization inhibition, and cool to room temperature to obtain the modified epoxy resin b3. After mixing the modified epoxy resins a3 and b3, the modified epoxy resin of Comparative Example 3 is obtained.

[0032] (2) Take 100 parts by weight of titanium dioxide with a particle size between 100 and 150 nm, place it in a high-speed stirring kettle, heat it to 90 °C, and then stir at a high speed (370 r / min) for 30 min to obtain the filler of Comparative Example 3.

[0033] (3)According to the coating formulation in Table 1, add the epoxy resin, filler, and other raw material components obtained in steps (1) and (2) respectively, and use a double planetary mixer to stir all the materials for 1 h to obtain the sample coating of Comparative Example 3.

[0034] Coating effect evaluation: 1. Coating resistance to ultraviolet corrosion protection performance test Apply the sample coating onto multiple frosted steel plates using a coater. Divide the cured frosted steel plates with the coating into two groups. For group a samples, directly conduct the film hardness test (characterized using Shore hardness), and after testing the hardness, immerse them in 5% brine for 200 h to observe the coating and rusting conditions. For group b samples, first irradiate them with a UV ultraviolet lamp for 300 h, then heat them in an 80 °C oven for 200 h, take them out, test the film hardness, and immerse them in 5% brine for 200 h, and then observe the coating conditions and rusting conditions after taking them out. The test results of the coating resistance to ultraviolet corrosion protection performance of the coatings prepared in Examples 1-2 and Comparative Examples 1-3 are shown in Table 2 below.

[0035] 2. Film mechanical property test The film mechanical property test mainly refers to conducting impact, tensile, and bending tests on the film, and the tests are respectively carried out with reference to ASTM D2794, ASTM D 2370, and ASTM D 522. The test results of the film mechanical properties of the coatings prepared in Examples 1-2 and Comparative Examples 1-3 are shown in Table 3 below.

[0036] Test results:

[0037] As can be seen from the results in Table 2 above, in group a, Examples 1, 2 and Comparative Example 2 have lower hardness than other groups, indicating better film flexibility. This is mainly because the filler contains dibenzo-21-crown-7 and polypropylene glycol, which enables the filler to be better dispersed and reduces the crosslinking degree between resin segments, increasing flexibility. After ultraviolet and high-temperature aging, the film surface hardness of Comparative Examples 1 and 2 increased significantly, and cracking has occurred. This is mainly because the resin used was not modified for resistance to ultraviolet and heat, resulting in the degradation of the resin under extreme conditions and losing its effectiveness.

[0038]

[0039] It can be seen from the mechanical property test data in Table 3 that the films of the coatings prepared in Examples 1-2 by the method of the present invention have better flexibility than the films of the comparative examples, and can ensure the integrity of the film under stronger impacts. It can be seen that the films of the coatings prepared by the method of the present invention have good mechanical properties, and the method of the present invention can effectively improve the film flexibility and anti-corrosion performance of the prepared epoxy resin coatings.

Claims

1. A method for preparing an anti-corrosion epoxy resin coating for steel structures in a marine environment, characterized in that: The following steps are involved: (1) Preparation of modified epoxy resin: ① According to weight, take 25-30 parts of bisphenol A, 65-70 parts of epoxy chloropropylene, 1-3 parts of p-hydroxybenzoic acid, and 1-3 parts of pyrrolidone and place them in a reaction kettle, heat to 150-160°C, and after the reactants are melted, add 0.2 parts of dimethylaniline, react for 5-6 hours under stirring, add sulfuric acid to neutralize the dimethylaniline, and cool to room temperature to obtain modified epoxy resin a; ② Take 25-30 parts of bisphenol A, 65-70 parts of epoxy chloropropylene, and 5-8 parts of methyl methacrylate by weight, place them in a reaction kettle, heat to 130-150°C, add 0.2 parts of benzoyl peroxide after the reactants melt, stir for 3-4 hours, add 0.1-0.2 parts of hydroquinone to inhibit polymerization, and cool to room temperature to obtain modified epoxy resin B; ③ The modified epoxy resin a and the modified epoxy resin b are mixed and stirred uniformly to obtain the modified epoxy resin; (2) Preparation of functional fillers: 95-100 parts by weight of titanium dioxide with a particle size of 100-150 nm are placed in a high-speed stirring kettle, heated to 80-90° C., and then 5-6 parts of dibenzo-21-crown-7 and 2-3 parts of polypropylene glycol are added in sequence, and stirred at high speed for 30-40 minutes to obtain a functional filler; (3) Take 55-60 parts by weight of modified epoxy resin; 18-20 parts by weight of curing agent; 15-17 parts by weight of solvent; 2-3 parts by weight of leveling agent; 3-5 parts by weight of 200-mesh butyl rubber particles; and 15-18 parts by weight of functional filler; use a double planetary mixer to mix and stir all the materials for 1 hour to prepare a coating.

2. The method for preparing the anticorrosive epoxy resin coating for steel structures in marine environments according to claim 1, characterized in that: In step (2), the high-speed stirring has a rotation speed of 300 to 400 r / min.

3. The method for preparing the anticorrosive epoxy resin coating for steel structure in marine environment according to claim 1, characterized in that: The curing agent in step (3) is selected from one or more of triethylenetetramine, diaminodiphenylmethane or 4,4'-diaminodiphenylmethane.

4. The method for preparing the anticorrosive epoxy resin coating for steel structures in marine environments according to claim 1, characterized in that: The solvent in step (3) is selected from one or more of xylene, dimethyl sulfoxide or toluene.

5. The method for preparing the anticorrosive epoxy resin coating for steel structures in marine environments according to claim 1, characterized in that: The leveling agent described in step (3) is selected from one or more of trifluorochlorosilane, polydimethylsiloxane or polyacrylate.

6. The epoxy resin coating prepared by the method for preparing an anti-corrosion epoxy resin coating for steel structures in marine environments as described in any one of claims 1 to 5.

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