Super-thick solvent-free epoxy coating for offshore steel pipe pile as well as preparation method and application of super-thick solvent-free epoxy coating

Abstract

The invention discloses an ultra-thick solvent-free epoxy coating for an offshore steel pipe pile as well as a preparation method and application of the ultra-thick solvent-free epoxy coating. The ultra-thick solvent-free epoxy coating is prepared from a component A and a component B, the component A comprises the following components in percentage by mass: 20-25% of epoxy resin, 20-25% of silicon branched modified epoxy resin, 2-5% of a reactive diluent, 10-20% of calcium carbonate, 10-20% of natural barium sulfate, 2-5% of graphene, 10-15% of glass flakes, 5-10% of silica powder, 5-10% of zinc phosphate, 0.8-2% of a thixotropic agent and 0.2-0.3% of a flatting agent; and the component B comprises 15-30% of a curing agent, 15-25% of talcum powder, 15-25% of natural barium sulfate, 10-15% of titanium dioxide, 5-10% of zinc phosphate and 0.2-0.3% of a leveling agent. According to the present invention, the adhesion, the salt resistance, the wear resistance and the aging resistance of the epoxy coating can be improved, and the epoxy coating can be used for the anti-corrosion coating of the offshore steel pipe pile close to or in contact with seawater.

Description

Technical Field

[0001] The invention relates to the technical field of coatings, and in particular to an ultra-thick solvent-free epoxy coating for offshore steel pipe piles and a preparation method thereof. Background Art

[0002] Offshore steel pipe columns are made of high-strength steel with good support and compression resistance. They are usually used to support and fix wind turbines, make platforms, and build cross-sea bridges at sea. When used at sea, a large amount of chloride ions (Cl-) electrolytes in seawater act as conductive media to cause electrochemical reactions on the surface of steel pipe piles, corroding steel. The metabolic activities of microorganisms in the marine environment, including sulfate-reducing bacteria and iron bacteria, change the chemical properties of the microenvironment around steel pipe piles and accelerate the corrosion of steel pipe piles. At the same time, the impact of waves and the friction of marine sediments will cause wear on the surface of steel pipe piles and accelerate corrosion.

[0003] Therefore, in order to ensure the long-term stability and durability of steel pipe piles in the marine environment, steel pipe piles need to undergo necessary anti-corrosion treatment. Common methods include coating with anti-corrosion paint, cathodic protection, and external coating materials, combined with the selection of pipe materials and consideration of design margins. Nowadays, the combination of coating with anti-corrosion paint and cathodic protection is a more common anti-corrosion strategy for offshore steel pipe piles. The coating efficiency of anti-corrosion paint and subsequent maintenance and construction are relatively convenient. However, cathodic protection will peel off the anti-corrosion coating on the surface of steel pipe piles.

[0004] With the increasing awareness of environmental protection, the research and development and application of marine anti-corrosion coatings pay more and more attention to environmental protection, low VOC, and low impact on marine ecology. In terms of function, it not only requires strong corrosion resistance, but also tends to have anti-fouling, wear resistance, low surface applicability, long weather resistance and other functions. Moreover, the coating system and construction technology of the anti-corrosion coating of offshore steel pipe piles need to be faster, more environmentally friendly, and more energy-saving. Therefore, the anti-corrosion coating of offshore steel pipe piles needs to develop in a more professional, environmentally friendly, and efficient direction.

[0005] At present, marine anti-corrosion coatings are in contact with seawater for a long time. Water molecules can diffuse through the organic coating to reach the coating-substrate interface. Water molecules replace the coating and interact with the substrate, causing the coating to lose adhesion, or water molecules and steel undergo electrochemical reactions at the interface between the two, causing the coating to lose its protective effect and accelerating the corrosion of the steel. Summary of the invention

[0006] In view of the problems existing in the background technology, the purpose of the present invention is to provide an ultra-thick solvent-free epoxy coating for offshore steel pipe piles, and a preparation method and application thereof. By adding a specific proportion of silicon-branched modified epoxy resin, the adhesion, salt resistance, wear resistance, aging resistance, high temperature resistance and mechanical strength of the epoxy coating can be improved, which is particularly suitable for seawater corrosion protection.

[0007] In order to achieve the above object, the present invention provides an ultra-thick solvent-free epoxy coating for offshore steel pipe piles, the raw materials of which include component A and component B; calculated by mass, component A includes:

[0008]

[0009] Component B includes:

[0010]

[0011] Optionally, the preparation method of the silicon-branched modified epoxy resin comprises the following steps: (1) adding ethyl acetate in sequence to a reaction kettle with a reflux device under inert gas protection, adding butyl methacrylate, glycidyl methacrylate and vinyl trimethoxysilane at room temperature, controlling the temperature of the reaction kettle to 80-100°C, adding a butyl acetate solution of the initiator dropwise under stirring, maintaining reflux, the reaction time is 2-4 hours, cooling to room temperature, and obtaining a pre-reaction liquid; (2) adding 3-glycidyloxypropyl trimethoxysilane to the pre-reaction liquid, stirring evenly, adding deionized water dropwise under stirring, controlling the temperature of the reaction kettle to be in the range of 50-70°C, the reaction time is 3-4 hours, heating to 100-110°C and continuing the reaction for 3-5 hours; (3) removing the reflux device, distilling and removing the solvent, washing with deionized water, filtering, and drying to obtain the silicon-branched modified epoxy resin.

[0012] Optionally, the molar ratio of butyl methacrylate, glycidyl methacrylate, vinyl trimethoxysilane, and 3-glycidyloxypropyl trimethoxysilane is 1-2:3-5:1:1-2.

[0013] Optionally, the curing agent is one or a combination of polyamide, polyetheramine, alkylphenolaldehydeamine and aliphatic polyamine.

[0014] Optionally, the active diluent is one or more of cyclohexane-1,2-dicarboxylic acid diglycidyl ester, neopentyl glycol diglycidyl ether, trimethylolpropane triglycidyl ether, and cyclohexanedimethanol diglycidyl ether.

[0015] Optionally, the epoxy resin is one or a combination of bisphenol A epoxy resin, phenolic modified epoxy resin, bisphenol F epoxy resin and acrylic modified epoxy resin.

[0016] Optionally, the initiator is one or a combination of diisocyanatobutyronitrile, dicumyl peroxide, sodium persulfate, and ammonium persulfate.

[0017] Optionally, the thixotropic agent is one or a combination of polyamide wax, fumed silica, and organic bentonite.

[0018] The present invention also provides a method for preparing an ultra-thick solvent-free epoxy coating for offshore steel pipe piles, comprising the following steps: (1) weighing epoxy resin, silicon-branched modified epoxy resin, reactive diluent, calcium carbonate, natural barium sulfate, graphene, glass flakes, silicon micropowder, zinc phosphate, thixotropic agent and leveling agent in parts by weight, heating in a reaction kettle to 50-70° C., rotating at 2500-3500 rpm, stirring for 0.5-1 h, standing, vacuumizing to remove bubbles, and discharging. , obtain a mixture component A; (2) weigh a curing agent, talcum powder, natural barium sulfate, titanium dioxide, zinc phosphate and a leveling agent according to weight, heat to 40-50°C in a reaction kettle, rotate at 2000-3000 rpm, stir for 0.5h, let stand, vacuum to remove bubbles, discharge, and obtain a mixture component B; (3) mix the above-mentioned mixture components A and B in a mass ratio of 1:1 to obtain an ultra-thick solvent-free epoxy coating for offshore steel pipe piles.

[0019] The present invention also provides a use of an ultra-thick solvent-free epoxy coating for offshore steel pipe piles, which is used for the anti-corrosion coating of offshore steel pipe piles adjacent to or in contact with seawater.

[0020] The present invention also provides a use of an ultra-thick solvent-free epoxy coating for offshore steel pipe piles, which can also be applied to ship hulls, offshore survey platforms, oil production platforms, offshore oil and gas gathering pipelines, port terminals or cross-sea bridges.

[0021] The beneficial effects of the present invention are as follows:

[0022] 1. First, butyl methacrylate, glycidyl methacrylate and vinyl trimethoxysilane are copolymerized to obtain a silicon-containing epoxy molecular chain grafted with an alkoxy group. Then, under hydrolysis conditions, the three alkoxy groups of the alkoxysilane and the alkoxy group of 3-glycidyloxypropyl trimethoxysilane undergo a multi-dimensional hydrolysis grafting reaction, which not only increases the epoxy group, but also forms a multi-dimensional grafted and cross-linked silicon atom-containing branched structure in the molecular structure. The study found that the silicon-branched modified epoxy resin synthesized by this method is used in seawater anti-corrosion epoxy coatings, which can significantly improve the adhesion, salt resistance, wear resistance, aging resistance, high temperature resistance and mechanical strength of the epoxy resin, and is particularly suitable for seawater anti-corrosion.

[0023] 2. The mass ratio of the two components of the epoxy coating of the present invention is 1:1, which is easy to measure, ensures the stability of construction, and is more suitable for automated spraying construction.

[0024] 3. The epoxy coating has excellent anti-corrosion performance and can meet the relevant test requirements of System 7A in NORSOKM501. The coating has good wear resistance and high hardness, and is suitable for use in offshore steel pipe pile splash zones.

[0025] 4. The product is non-toxic and complies with the relevant requirements of the "Sanitary Safety Evaluation Specification for Drinking Water Distribution Equipment and Protective Materials" (2001). It has no impact on the environment and does not affect the survival of marine life. The product is solvent-free, has good fineness, and the solid content can reach more than 99.5%. No heavy metals can be detected, which meets the requirements of "GB30981-2020".

[0026] 5. In view of the improved performance of the coating, the single film thickness of the product can reach 3000μm without cracking of the coating, which meets the requirement of more than 1000μm for offshore steel pipe piles and improves construction efficiency. DETAILED DESCRIPTION

[0027] In order to make the above-mentioned objects, features and advantages of the invention more obvious and easy to understand, the specific embodiments of the invention are described in detail below.

[0028] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0029] According to the present invention, an ultra-thick solvent-free epoxy coating for offshore steel pipe piles comprises raw materials including component A and component B. Calculated by weight, component A comprises:

[0030]

[0031]

[0032] Component B includes:

[0033]

[0034] In one embodiment, the preparation method of the silicon-branched modified epoxy resin comprises the following steps: (1) adding ethyl acetate in sequence to a reaction kettle with a reflux device under inert gas protection, adding butyl methacrylate, glycidyl methacrylate, and vinyl trimethoxysilane at room temperature, controlling the temperature of the reaction kettle to 80-100° C., adding a butyl acetate solution of an initiator dropwise under stirring, maintaining reflux, and reacting for 2-4 hours, cooling to room temperature, and obtaining a pre-reaction liquid; (2) adding 3-glycidyloxypropyl trimethoxysilane to the pre-reaction liquid, stirring evenly, adding deionized water dropwise under stirring, controlling the temperature of the reaction kettle to be in the range of 50-70° C., the reaction time is 3-4 hours, and heating to 100-110° C. and continuing the reaction for 3-5 hours; (3) removing the reflux device, distilling and removing the solvent, washing with deionized water, filtering, and drying to obtain the silicon-branched modified epoxy resin.

[0035] In one embodiment, the molar ratio of butyl methacrylate, glycidyl methacrylate, vinyl trimethoxysilane, and 3-glycidyloxypropyl trimethoxysilane is 1-2:3-5:1:1-2

[0036] In one embodiment, the curing agent is one or a combination of polyamide, polyetheramine, alkylphenolaldehydeamine and aliphatic polyamine.

[0037] In one embodiment, the active diluent is one or more of cyclohexane-1,2-dicarboxylic acid diglycidyl ester, neopentyl glycol diglycidyl ether, trimethylolpropane triglycidyl ether, and cyclohexanedimethanol diglycidyl ether.

[0038] In one embodiment, the epoxy resin is one or a combination of bisphenol A epoxy resin, phenolic modified epoxy resin, bisphenol F epoxy resin and acrylic modified epoxy resin.

[0039] In one embodiment, the initiator is one or a combination of diisocyanatobutyronitrile, dicumyl peroxide, sodium persulfate, and ammonium persulfate.

[0040] In one embodiment, the thixotropic agent is one or a combination of polyamide wax, fumed silica, and organic bentonite.

[0041] The present invention also provides a method for preparing an ultra-thick solvent-free epoxy coating for offshore steel pipe piles, comprising the steps of: (1) weighing epoxy resin, silicon-branched modified epoxy resin, reactive diluent, calcium carbonate, natural barium sulfate, graphene, glass flakes, silicon micropowder, zinc phosphate, thixotropic agent and leveling agent in parts by weight, heating in a reaction kettle to 50-70° C., rotating at 2500-3500 rpm, stirring for 0.5-1 h, standing, vacuumizing to remove bubbles, and discharging. Obtain a mixture component A; (2) weigh a curing agent, talcum powder, natural barium sulfate, titanium dioxide, zinc phosphate and a leveling agent in parts by weight, heat in a reaction kettle to 40-50° C., rotate at 2000-3000 rpm, stir for 0.5 h, let stand, evacuate to remove bubbles, discharge, and obtain a mixture component B; (3) Evenly mix the above-mentioned mixture components A and B in a mass ratio of 1:1 to obtain an ultra-thick solvent-free epoxy coating for offshore steel pipe piles.

[0042] The present invention also provides a use of an ultra-thick solvent-free epoxy coating for offshore steel pipe piles, which is used for anti-corrosion coatings of offshore steel pipe piles that are adjacent to or in contact with seawater. The present invention can be applied to solvent-free epoxy coatings in splash zones, tidal range zones, and underwater zones of offshore steel pipe columns. The coating can protect the steel pipe piles, avoid electrochemical corrosion, accelerated corrosion by seawater and scouring forces, and the corrosion effects of microorganisms, and ensure the long-term and safe use of steel pipe piles. At the same time, the film thickness of the invented product can reach 3000μm after one spraying, which meets the 1000μm thickness required for the anti-corrosion of steel pipe columns, improves construction efficiency, reduces energy consumption, reduces emissions, and is more environmentally friendly. The present invention does not contain VOCs or heavy metals, and has less impact on the marine environment.

[0043] The present invention also provides a use of an ultra-thick solvent-free epoxy coating for offshore steel pipe piles, which can also be applied to ship hulls, offshore survey platforms, oil production platforms, offshore oil and gas gathering pipelines, port terminals or cross-sea bridges.

[0044] The following is a detailed description of the ultra-thick solvent-free epoxy coating for offshore steel pipe piles of the present invention and its preparation method and application through examples. Main raw materials and equipment used: Unless otherwise specified, the raw materials and equipment of each embodiment and comparative example are the same; materials without specific models or types are sourced from the market or the common same models available through common channels, and are not specifically limited.

[0045] Example 1

[0046] 1. Preparation of silicon-branched modified epoxy resin

[0047] (1) Ethyl acetate was added to a reaction kettle with a reflux device under inert gas protection, and butyl methacrylate, glycidyl methacrylate, and vinyl trimethoxysilane were added at room temperature. The temperature of the reaction kettle was controlled at 80° C., and a butyl acetate solution of diisodiazobutyronitrile was added dropwise under stirring. The reflux was maintained for a reaction time of 2 h. After cooling to room temperature, a pre-reaction solution was obtained.

[0048] (2) adding 3-glycidyloxypropyltrimethoxysilane to the pre-reaction liquid, stirring evenly, adding deionized water dropwise under stirring, controlling the temperature of the reactor within the range of 50° C., the reaction time is 3 h, and heating to 100° C. to continue the reaction for 3 h; the molar ratio of butyl methacrylate, glycidyl methacrylate, vinyl trimethoxysilane, and 3-glycidyloxypropyltrimethoxysilane is 1:3:1:1;

[0049] (3) removing the reflux device, distilling and removing the solvent, washing with deionized water, filtering, and drying to obtain a silicon-branched modified epoxy resin.

[0050] 2. Preparation of solvent-free epoxy coating

[0051] (1) Weigh 20 parts of acrylic modified epoxy resin, 20 parts of silicon-branched modified epoxy resin, 2 parts of cyclohexane-1,2-dicarboxylic acid diglycidyl ester, 10 parts of calcium carbonate, 10 parts of natural barium sulfate, 2 parts of graphene, 10 parts of glass flakes, 5 parts of silicon powder, 5 parts of zinc phosphate, 0.8 parts of fumed silica and 0.2 parts of leveling agent (BYK-348) in parts by weight, heat to 50° C. in a reaction kettle, rotate at 2500 rpm, stir for 0.5 h, let stand, evacuate to remove bubbles, discharge, and obtain a mixed material component A;

[0052] (2) Weigh 15 parts of polyetheramine, 15 parts of talc, 15 parts of natural barium sulfate, 10 parts of titanium dioxide, 5 parts of zinc phosphate and 0.2 parts of leveling agent (BYK-348) by weight, heat to 40° C. in a reaction kettle, rotate at 2000 rpm, stir for 0.5 h, let stand, evacuate to remove bubbles, discharge, and obtain a mixed material component B;

[0053] (3) The above-mentioned mixed material component A and component B are mixed uniformly in a mass ratio of 1:1 to obtain a solvent-free epoxy coating.

[0054] Example 2

[0055] 1. Preparation of silicon-branched modified epoxy resin

[0056] (1) Ethyl acetate was added to a reaction kettle with a reflux device under inert gas protection, and butyl methacrylate, glycidyl methacrylate, and vinyl trimethoxysilane were added at room temperature. The temperature of the reaction kettle was controlled at 100° C., and a butyl acetate solution of diisopropyl peroxide was added dropwise under stirring. The reflux was maintained for a reaction time of 4 hours. After cooling to room temperature, a pre-reaction solution was obtained.

[0057] (2) adding 3-glycidyloxypropyltrimethoxysilane to the pre-reaction liquid, stirring evenly, adding deionized water dropwise under stirring, controlling the temperature of the reactor within the range of 70° C., the reaction time is 4 hours, heating to 110° C. and continuing the reaction for 5 hours; the molar ratio of butyl methacrylate, glycidyl methacrylate, vinyl trimethoxysilane and 3-glycidyloxypropyltrimethoxysilane is 2:5:1:2;

[0058] (3) removing the reflux device, distilling and removing the solvent, washing with deionized water, filtering, and drying to obtain a silicon-branched modified epoxy resin.

[0059] 2. Preparation of solvent-free epoxy coating

[0060] (1) Weigh 25 parts of acrylic modified epoxy resin, 25 parts of silicon-branched modified epoxy resin, 5 parts of neopentyl glycol diglycidyl ether, 20 parts of calcium carbonate, 20 parts of natural barium sulfate, 5 parts of graphene, 15 parts of glass flakes, 10 parts of silicon powder, 10 parts of zinc phosphate, 2 parts of fumed silica and 0.3 parts of leveling agent (BYK-348) in parts by weight, heat to 70° C. in a reaction kettle, rotate at 3500 rpm, stir for 1 h, let stand, evacuate to remove bubbles, discharge, and obtain a mixed material component A;

[0061] (2) Weigh 30 parts of polyamide, 25 parts of talc, 25 parts of natural barium sulfate, 15 parts of titanium dioxide, 10 parts of zinc phosphate and 0.3 parts of leveling agent (BYK-348) by weight, heat to 50° C. in a reaction kettle, rotate at 3000 rpm, stir for 0.5 h, let stand, evacuate to remove bubbles, discharge, and obtain a mixed material component B;

[0062] (3) The above-mentioned mixed material component A and component B are mixed uniformly in a mass ratio of 1:1 to obtain a solvent-free epoxy coating.

[0063] Example 3

[0064] 1. Preparation of silicon-branched modified epoxy resin

[0065] (1) Ethyl acetate was added to a reaction kettle with a reflux device under inert gas protection, and butyl methacrylate, glycidyl methacrylate, and vinyl trimethoxysilane were added at room temperature. The temperature of the reaction kettle was controlled at 90° C., and a butyl acetate solution of diisopropyl peroxide was added dropwise under stirring. The reflux was maintained, and the reaction time was 3 h. After cooling to room temperature, a pre-reaction solution was obtained;

[0066] (2) adding 3-glycidyloxypropyltrimethoxysilane to the pre-reaction liquid, stirring evenly, adding deionized water dropwise under stirring, controlling the temperature of the reactor within the range of 60° C., the reaction time is 3.5 h, heating to 105° C. and continuing the reaction for 4 h; the molar ratio of butyl methacrylate, glycidyl methacrylate, vinyl trimethoxysilane, and 3-glycidyloxypropyltrimethoxysilane is 1.5:4:1:1.5;

[0067] (3) removing the reflux device, distilling and removing the solvent, washing with deionized water, filtering, and drying to obtain a silicon-branched modified epoxy resin.

[0068] 2. Preparation of solvent-free epoxy coating

[0069] (1) Weigh 22.5 parts of acrylic modified epoxy resin, 23 parts of silicon-branched modified epoxy resin, 3.5 parts of trimethylolpropane triglycidyl ether, 15 parts of calcium carbonate, 15 parts of natural barium sulfate, 3.5 parts of graphene, 12 parts of glass flakes, 8 parts of silicon powder, 7 parts of zinc phosphate, 1.5 parts of fumed silica and 0.25 parts of leveling agent (BYK-348) in parts by weight, heat to 60° C. in a reaction kettle, rotate at 3000 rpm, stir for 50 min, let stand, evacuate to remove bubbles, discharge, and obtain a mixed material component A;

[0070] (2) Weigh 18 parts of polyamide, 16 parts of talc, 17 parts of natural barium sulfate, 12 parts of titanium dioxide, 8 parts of zinc phosphate and 0.25 parts of leveling agent (BYK-348) by weight, heat to 45° C. in a reaction kettle, rotate at 2500 rpm, stir for 0.5 h, let stand, evacuate to remove bubbles, discharge, and obtain a mixed material component B;

[0071] (3) The above-mentioned mixed material component A and component B are mixed uniformly in a mass ratio of 1:1 to obtain a solvent-free epoxy coating.

[0072] Comparative Example 1

[0073] 1. Preparation of silicon-branched modified epoxy resin

[0074] (1) Ethyl acetate was added to a reaction kettle with a reflux device under inert gas protection in sequence, and butyl methacrylate, glycidyl methacrylate, and vinyl trimethoxysilane were added at room temperature. The temperature of the reaction kettle was controlled at 90° C., and a butyl acetate solution of the initiator was added dropwise under stirring. The reflux was maintained. The reaction time was 3 hours. After cooling to room temperature, a pre-reaction solution was obtained. The molar ratio of butyl methacrylate, glycidyl methacrylate, and vinyl trimethoxysilane was 1.5:4:1.

[0075] (2) removing the reflux device, distilling and removing the solvent, washing with deionized water, filtering, and drying to obtain a silane-modified epoxy resin.

[0076] 2. Preparation of solvent-free epoxy coating

[0077] Except that the silicon-branched modified epoxy resin is replaced by an equal amount of silane-modified epoxy resin, the other steps are the same as those in Example 3.

[0078] Comparative Example 2

[0079] Except that the silicon-branched modified epoxy resin is not added, the other steps are the same as those in Example 3.

[0080] Performance Testing

[0081] The specific test standards and test data are shown in Table 1.

[0082] Table 1 Test results

[0083]

[0084]

[0085]

[0086]

[0087] It can be seen from the data of the embodiments and comparative examples that the present invention uses a copolymerization reaction to graft epoxy with a molecular chain containing alkoxy groups and silicon, and then undergoes a multi-dimensional hydrolysis grafting reaction with the alkoxy groups of 3-glycidyloxypropyltrimethoxysilane to obtain a silicon-branched modified epoxy resin, which is added to a solvent-free epoxy coating to significantly improve its adhesion, salt resistance, wear resistance, aging resistance, high temperature resistance and mechanical strength, etc., and is particularly suitable for anti-corrosion coatings for offshore steel pipe piles.

[0088] The above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. An ultra-thick solvent-free epoxy coating for offshore steel pipe piles, characterized in that: The raw materials include component A and component B; Calculated by mass, component A includes: Component B includes:

2. The ultra-thick solvent-free epoxy coating for offshore steel pipe piles according to claim 1, characterized in that: The preparation method of the silicon-branched modified epoxy resin comprises the following steps: (1) Ethyl acetate is added sequentially to a reaction kettle with a reflux device under inert gas protection, and butyl methacrylate, glycidyl methacrylate, and vinyl trimethoxysilane are added at room temperature. The temperature of the reaction kettle is controlled at 80-100° C., and a butyl acetate solution of the initiator is added dropwise under stirring. The reflux is maintained, and the reaction time is 2-4 hours. After cooling to room temperature, a pre-reaction solution is obtained; (2) adding 3-glycidyloxypropyltrimethoxysilane to the pre-reaction liquid, stirring evenly, adding deionized water dropwise under stirring, controlling the temperature of the reaction kettle within the range of 50-70° C., the reaction time is 3-4 h, and heating to 100-110° C. to continue the reaction for 3-5 h; (3) removing the reflux device, distilling and removing the solvent, washing with deionized water, filtering, and drying to obtain a silicon-branched modified epoxy resin.

3. The ultra-thick solvent-free epoxy coating for offshore steel pipe piles according to claim 2, characterized in that: The molar ratio of butyl methacrylate, glycidyl methacrylate, vinyl trimethoxysilane and 3-glycidyloxypropyl trimethoxysilane is 1-2:3-5:1:1-2 4. The ultra-thick solvent-free epoxy coating for offshore steel pipe piles according to claim 1, characterized in that: The curing agent is one or a combination of polyamide, polyetheramine, alkylphenolaldehydeamine and aliphatic polyamine.

5. The ultra-thick solvent-free epoxy coating for offshore steel pipe piles according to claim 1, characterized in that: The active diluent is one or more of cyclohexane-1,2-dicarboxylic acid diglycidyl ester, neopentyl glycol diglycidyl ether, trimethylolpropane triglycidyl ether, and cyclohexanedimethanol diglycidyl ether.

6. The ultra-thick solvent-free epoxy coating for offshore steel pipe piles according to claim 1, characterized in that: The epoxy resin is one or a combination of bisphenol A epoxy resin, phenolic modified epoxy resin, bisphenol F epoxy resin and acrylic modified epoxy resin.

7. The ultra-thick solvent-free epoxy coating for offshore steel pipe piles according to claim 1, characterized in that: The initiator is one or a combination of diisocyanatobutyronitrile, dicumyl peroxide, sodium persulfate and ammonium persulfate.

8. The method for preparing the ultra-thick solvent-free epoxy coating for offshore steel pipe piles according to any one of claims 1 to 7, characterized in that: The method comprises the following steps: (1) weighing epoxy resin, silicon-branched modified epoxy resin, active diluent, calcium carbonate, natural barium sulfate, graphene, glass flakes, silicon powder, zinc phosphate, thixotropic agent and leveling agent in parts by weight, heating the mixture to 50-70°C in a reaction kettle, rotating at a speed of 2500-3500 rpm, stirring for 0.5-1h, standing, vacuumizing and defoaming, discharging, and obtaining a mixture component A; (2) weighing curing agent, talcum powder, natural barium sulfate, titanium dioxide, zinc phosphate and leveling agent in parts by weight, heating the mixture to 40-50°C in a reaction kettle, rotating at a speed of 2000-3000 rpm, stirring for 0.5h, standing, vacuumizing and defoaming, discharging, and obtaining a mixture component B; and (3) mixing the above-mentioned mixture components A and B in a mass ratio of 1:1 to obtain an ultra-thick solvent-free epoxy coating for offshore steel pipe piles.

9. Use of the ultra-thick solvent-free epoxy coating for offshore steel pipe piles according to any one of claims 1 to 7 or the ultra-thick solvent-free epoxy coating for offshore steel pipe piles obtained by the preparation method according to claim 8, characterized in that: Anti-corrosion coating for offshore steel pipe piles near or in contact with seawater.

10. The ultra-thick solvent-free epoxy coating for offshore steel pipe piles according to any one of claims 1 to 7 or the The use of the ultra-thick solvent-free epoxy coating for offshore steel pipe piles obtained by the preparation method described in claim 8 is characterized in that: It is also used in ship hulls, offshore survey platforms, oil production platforms, offshore oil and gas pipelines, port terminals or cross-sea bridges.

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