Preparation method of multi-point interpenetrating cross-linking self-repairing polyurea microcapsule modified epoxy coating

Abstract

The present invention discloses a method for preparing a multi-point interpenetrating cross-linked self-repairing polyurea microcapsule modified epoxy coating. Graphene oxide is modified by isocyanate groups and used as a water phase to prepare a Pickering emulsion with an oil phase formed by isocyanate, diamine and a repair agent. The microcapsule shell in the emulsion is fully cured by initiating in-situ polymerization. Graphene oxide is introduced to the surface of the microcapsule by chemical grafting, and the epoxy resin is subjected to organic silicone flexibility modification. Finally, the multi-site self-repairing microcapsules and the modified epoxy resin are subjected to a chemical cross-linking reaction with isocyanate and diamine by addition polymerization to prepare a self-repairing polyurea microcapsule modified epoxy coating. The epoxy coating prepared by the present invention solves the problem that the existing polyurea microcapsules are added as fillers to the epoxy coating matrix, which affects the performance of the epoxy coating and reduces the service life and mechanical properties of the coating.

Description

Technical Field

[0001] The present invention belongs to the technical field of coating material preparation methods, and specifically relates to a preparation method of a multi-point interpenetrating cross-linked self-repairing polyurea microcapsule modified epoxy coating. Background Art

[0002] Microcapsules refer to nanofillers that encapsulate trace amounts of substances in polymer films. They are a micro-packaging technology for storing solids, liquids, and gases. They have the characteristics of simple preparation, low cost, and easy control of microcapsule size. Microcapsules can improve the stability of the product, prevent mutual interference between various components, effectively reduce the reaction of active substances to external environmental factors, and reduce the diffusion and evaporation of core materials into the environment. The Pickering emulsion method can stabilize the emulsion by forming a stable interfacial film on the liquid interface using solid particles (Pickering particles). This method can replace traditional emulsifiers and has good stability and controllability. It is a method for preparing microcapsules with simple equipment, low cost, and can coat a variety of core materials. The preparation of polyurea microcapsules by in situ polymerization reaction has the characteristics of moderate reaction speed, high core material coverage, and self-healing shell layer. At the same time, different core materials can be added inside to achieve antibacterial and anti-corrosion effects.

[0003] Epoxy resins offer excellent corrosion resistance, electrical insulation, and strength, as well as excellent processability, including strong adhesion, room-temperature operation, and simple construction. Epoxy resins are widely used in protective coatings due to the physical barrier effect of the epoxy matrix, preventing corrosive agents from reaching the substrate. However, epoxy resins have several significant drawbacks, such as cross-linking brittleness and micropores formed by solvent evaporation. Recent research has shown that epoxy resins can be modified by adding nanofillers, effectively filling these micropores and enhancing the physical and chemical barrier properties, thus improving the corrosion resistance of epoxy coatings. Therefore, the development of highly effective epoxy-based polyurea microcapsules with excellent mechanical properties is highly desirable for protective coatings.

[0004] The Chinese patent "A Method for Preparing Bishell Polyurea-Chitosan Microcapsules with pH-Responsive Antimicrobial Drug Release" (Application Number: 202310031093.3, Publication Number: CN115957196A, Announcement Date: April 14, 2023) discloses a method for preparing bishell polyurea-chitosan microcapsules with pH-responsive antimicrobial drug release. The method involves first preparing a drug-coated polyurea core material using interfacial polymerization. The resulting single-layer microcapsules are then coated with a diphenol-modified chitosan layer. However, issues such as release efficiency and damage to the bishell shell material hinder effective release of the core material from the microcapsules.

[0005] The Chinese patent "Anti-slip Deck Coating and Preparation Method Thereof" (Application Number: CN202210030893.9, Authorization Number: CN114350245B, Publication Number: CN114350245A) discloses an anti-slip deck coating and its preparation method. Boron phosphide-modified polyurea microcapsules are simultaneously polymerized with polyurea-polyurethane to form an interpenetrating network structure of polyurea microcapsules-polyurethane. Zirconia is then encapsulated with bisphenol A diglycidyl ether to form a denser network structure. However, the microcapsules are only cross-linked with the polyurea-polyurethane matrix, and the core material lacks other multifunctional release properties such as sterilization and corrosion protection.

[0006] Li et al. (Li H, Feng Y, Cui Y, et al. Polyurea / polyaniline hybrid shell microcapsules loaded with isophorone diisocyanate for synergetic self-healing coatings[J]. Progress in Organic Coatings, 2020, 145: 105684.) successfully synthesized polyurea / polyaniline (PU / PANI) hybrid shell microcapsules with isophorone diisocyanate (IPDI) as the core material by combining Pickering emulsion formation and interfacial polymerization. The self-healing coating containing 10wt% IPDI-loaded PU / PANI microcapsules showed significant repair ability and corrosion protection against microcracks after immersion in 10wt% NaCl solution for 30 days. However, the repair function of this coating is only provided by the external-aided polyurea / polyaniline (PU / PANI) hybrid shell microcapsules. The bonding performance between the microcapsules and the coating matrix is ​​low, which causes the mechanical properties of the coating to decline. At the same time, the self-healing effect of the coating is also limited by the content and distribution of the microcapsules. Summary of the Invention

[0007] The purpose of the present invention is to provide a method for preparing a multi-point interpenetrating cross-linking self-repairing polyurea microcapsule modified epoxy coating, which solves the problem that the existing polyurea microcapsules are added as fillers to the epoxy coating matrix, have poor bonding performance, thereby affecting the performance of the epoxy coating and causing the coating to have reduced service life and mechanical properties.

[0008] The technical solution adopted by the present invention is: a preparation method of a multi-point interpenetrating cross-linking self-healing polyurea microcapsule modified epoxy coating, wherein graphene oxide is modified by isocyanate groups to obtain isocyanate graphene oxide NCO-GO, and NCO-GO is used as the aqueous phase to prepare a Pickering emulsion with an oil phase formed by isocyanate, diamine and a repair agent; the polyurea microcapsule shell in the emulsion is fully cured by initiating in-situ polymerization; graphene oxide is introduced into the microcapsule surface by chemical grafting, and the epoxy resin is subjected to silicone flexibility modification; finally, the multi-site self-healing microcapsules and the modified epoxy resin are chemically cross-linked with isocyanate and diamine by addition polymerization to prepare a self-healing polyurea modified epoxy resin coating with multi-site graphene oxide microcapsules.

[0009] The technical solution adopted by the present invention is also characterized in that:

[0010] Furthermore, the preparation method of the multi-point interpenetrating cross-linked self-repairing polyurea microcapsule modified epoxy coating is specifically implemented according to the following steps:

[0011] Step 1, preparation of functional group-modified graphene oxide:

[0012] A certain amount of graphene oxide is mixed with isocyanate and functionalized under certain reaction conditions to obtain isocyanate-functionalized graphene oxide, namely isocyanate graphene oxide NCO-GO.

[0013] Step 2, prepare the water phase and the oil phase:

[0014] Weigh a certain amount of NCO-GO prepared in step 1 into deionized water, heat it to a certain temperature, and stir and disperse it thoroughly to obtain an aqueous phase;

[0015] Add isocyanate, diamine and repair agent into a beaker, stir and dissolve them under certain conditions to form a uniform phase to obtain an oil phase;

[0016] Step 3, prepare Pickering emulsion:

[0017] The aqueous phase and the oil phase prepared in step 2 are stirred in a certain manner, at a certain stirring rate and at a certain stirring temperature to prepare a Pickering emulsion, and the pH value of the emulsion and the amount of NCO-GO added are adjusted to obtain an emulsion;

[0018] Step 4: Preparation of multi-site self-repairing microcapsules:

[0019] The Pickering emulsion obtained in step 3 is slowly stirred under certain pH and temperature conditions to initiate an in-situ polymerization reaction for a period of time to fully solidify the polyurea microcapsule shell. After the reaction period, a certain amount of the aqueous solution of the Pickering emulsion prepared in step 3 is added to graft NCO-GO onto the microcapsule surface. The fully reacted solution is then centrifuged, washed, and dried to obtain multi-site self-healing microcapsules.

[0020] Step 5: Preparation of flexible modified epoxy resin:

[0021] A certain amount of amino-terminated organosilicon is mixed with epoxy resin, added to a solvent, and group modified under certain temperature and reaction time conditions to obtain an amino-terminated organosilicon-modified epoxy resin;

[0022] Step 6: Prepare a multi-point interpenetrating cross-linked modified epoxy resin coating:

[0023] The multi-site self-healing microcapsules obtained in step 4 and the amino-terminated modified epoxy resin prepared in step 5 are reacted with isocyanate and diamine by addition polymerization under certain conditions in the presence of a catalyst to prepare a self-healing polyurea-modified epoxy resin coating with multi-site NCO-GO microcapsules.

[0024] Furthermore, the isocyanate in step 1 is any one or more of isophorone diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, and xylene diisocyanate.

[0025] Furthermore, in step 1, graphene oxide is mixed with isocyanate at a ratio of 2.5 wt% to 10 wt%, nitrogen is used as a protective atmosphere during the reaction, the reaction temperature is 50 to 60° C., and the reaction time is 2 to 3 h to obtain isocyanate-terminated graphene oxide NCO-GO.

[0026] Furthermore, in step 2, the stirring temperature of the aqueous phase is 25° C. to 50° C., and the content of graphene oxide NCO-GO is 1 wt % to 5 wt %.

[0027] Furthermore, in step 2, the isocyanate in the oil phase is any one or more of isophorone diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, and xylene diisocyanate; the diamine is any one or more of diethylenetriamine, hexamethylenetetramine, ethylenediamine, triethylenediamine, and 1,6-hexanediamine; the repair agent is any one or more of epoxy resin, isocyanate, tung oil, and linseed oil; a mixture of isocyanate and diamine is used as the shell material, and the addition ratio of the two is 1:1; the repair agent is used as the core material, and the ratio of shell material to core material is 2 to 3:1, and the temperature when the oil phase is stirred and dissolved is 30°C to 40°C.

[0028] Furthermore, the parameters for preparing the Pickering emulsion in step 3 are: the ratio of the oil phase to the water phase is 1:3-9, the pH value of the solution during stirring is 2-5, the stirring method is any one of magnetic stirring, stirring paddle, and homogenizer, the stirring rate is 1000-3000 rpm, and the stirring temperature is 25°C-40°C.

[0029] Furthermore, the specific operation for preparing multi-site self-healing microcapsules in step 4 is as follows: adjusting the speed of the Pickering emulsion to 500-800 rpm, slowly heating it to 60-70°C, adjusting the pH value to 2-5, and continuing the reaction for 2-3 hours to fully solidify the shell material to obtain a microcapsule suspension, adding the aqueous solution prepared in step 3 to the microcapsule suspension, and the mass of the added aqueous solution is 0.3-0.5 times the aqueous phase of the Pickering emulsion prepared in step 3. The reaction is continued for 2-3 hours to complete the NCO-GO grafting; then, the centrifuged microcapsules are fully washed with anhydrous ethanol, acetone and deionized water, and finally the obtained microcapsules are placed in a vacuum oven and vacuum dried for 24-48 hours to obtain multi-site self-healing microcapsules.

[0030] Furthermore, in step 5, the epoxy resin is any one or more of E-03, E-12, E-20, diaminodiphenylmethane tetraglycidylamine, diglycidyl p-aminophenol, and 3-ESL aminomethylcyclohexane; the organosilicon is any one or more of amino-terminated polydimethylsiloxane, amino-terminated polydiethylsiloxane, and amino-terminated polymethylphenylsiloxane; and the solvent is any one or more of ethyl acetate, N,N-dimethylformamide, and anhydrous ethanol;

[0031] The specific parameters are: the amino-terminated silicone and the epoxy resin are mixed in a ratio of 0.5 to 1:1, the solvent addition amount is 10 wt% to 20 wt%, the stirring method is magnetic stirring, the stirring rate is 300 to 500 rpm, the reaction temperature is 70°C to 80°C, and the reaction time is 3h to 6h; the fully reacted amino-terminated modified epoxy resin is fully dried in a vacuum drying oven to remove the solvent to obtain the amino-terminated modified epoxy resin.

[0032] Furthermore, when preparing the multi-point interpenetrating cross-linked modified epoxy resin coating in step 6, the addition ratio of the amino-terminated modified epoxy resin, isocyanate and diamine is 1 to 3:1:1, the isocyanate is any one or more of isophorone diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, and xylene diisocyanate; the diamine is any one or more of diethylenetriamine, hexamethylenetetramine, ethylenediamine, triethylenediamine, and 1,6-hexanediamine; the solvent is any one or more of ethyl acetate, N,N-dimethylformyl, and anhydrous ethanol; and the catalyst is dibutyltin dilaurate;

[0033] The specific operation is as follows: adding the prepared multi-site self-healing microcapsules to a polyurea-modified epoxy resin matrix at a ratio of 1.5wt% to 4.5wt%; adding terminal amino-modified epoxy resin, isocyanate and diamine as raw materials for the addition reaction, and adding 10wt% to 20wt% of solvent and 0.02wt% to 0.04wt% of catalyst, polymerizing for 3 to 6 hours at a reaction temperature of 70 to 80°C, stirring by magnetic stirring, and stirring at a rate of 300 to 500rpm; removing the solvent in the modified epoxy resin by drying in a vacuum drying oven, and finally curing at 70 to 80°C for 24 to 48 hours to obtain a multi-point interpenetrating cross-linked modified self-healing microcapsule epoxy resin coating.

[0034] The beneficial effects of the present invention are:

[0035] The present invention provides a method for preparing a multi-point interpenetrating cross-linked self-repairing polyurea microcapsule modified epoxy coating. First, graphene oxide (NCO-GO) is modified with isocyanate groups and grafted onto the surface of the polyurea microcapsules by in-situ polymerization. This forms interpenetrating cross-linking reaction sites in the amino-modified epoxy resin matrix, improves the interfacial bonding of the microcapsules in the coating, and enhances the integrity and mechanical properties of the epoxy coating.

[0036] The epoxy coating prepared by the present invention not only enhances the coating's physical barrier effect and corrosion resistance by introducing NCO-GO, but also its isocyanate groups improve the dispersion of graphene oxide in the epoxy matrix and reduce graphene oxide aggregation. Subsequently, leveraging the Pickering emulsion method's advantages of good interfacial stability and emulsion size control, microcapsules are formed by in situ polymerization in an oil phase. The loading of a repair agent enables the microcapsules to self-heal. Simultaneously, the types of isocyanate and diamine are adjusted to increase the dynamic hydrogen bond density of the microcapsules, enabling long-term, controlled release of the core material.

[0037] The epoxy coating prepared by the present invention introduces NCO / GO modified microcapsules as external-aid repair agents into the amino-modified epoxy matrix, synergistically interacting with the dynamic polyurea molecular network in the modified epoxy matrix to construct a multi-point interpenetrating cross-linked molecular structure, achieving a mechanism of action that combines both intrinsic and external-aid self-repair, thereby improving the service life and healing efficiency of the coating. At the same time, by modifying the epoxy coating with organosilicon, the brittleness of the matrix can be effectively improved, defects generated during the curing process can be reduced, and the protective properties of the epoxy resin can be improved. Amino-active groups are introduced into the epoxy matrix to enable the matrix to bind to the NCO-GO interface. At the same time, as amine reaction monomers, they participate in the polymerization reaction of isocyanate and diamine, thereby forming an interpenetrating cross-linked molecular network internally, improving the mechanical properties of the epoxy resin, and giving the epoxy resin matrix a dynamic self-repairing function, forming a synergistic repair effect with the external-aid self-repairing microcapsules, and avoiding problems such as brittleness and cracking after curing.

[0038] In the epoxy coating prepared by the present invention, NCO-GO and microcapsules can produce a synergistic effect, acting as a second-phase reinforcement pinned to the damaged parts of the coating to improve the protective effect. It has broad application prospects in coating repair, extending coating life, enhancing mechanical properties, reducing epoxy resin brittleness, and improving protective effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a schematic diagram of the morphology of the multi-point interpenetrating cross-linked self-repairing polycapsule urea micro-modified epoxy coating prepared by the present invention. DETAILED DESCRIPTION

[0040] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0041] The present invention provides a method for preparing a multi-point interpenetrating cross-linked self-repairing polyurea microcapsule modified epoxy coating. Graphene oxide is modified by isocyanate groups to obtain isocyanate graphene oxide (NCO-GO), which is then grafted onto the surface of the polyurea microcapsule by in-situ polymerization. This forms interpenetrating cross-linking reaction sites in the amino-modified epoxy resin matrix, improves the interfacial bonding of the microcapsules in the coating, and enhances the integrity and mechanical properties of the epoxy coating.

[0042] Graphene oxide was functionalized with isocyanate, and a Pickering emulsion was prepared using NCO-GO as the aqueous phase and the oil phase formed by isocyanate, diamine, and a repair agent. Under certain conditions, in-situ polymerization was initiated to fully cure the polyurea microcapsule shell in the emulsion. Graphene oxide was then introduced onto the microcapsule surface via chemical grafting, while the epoxy resin was modified with silicone to make it flexible. Finally, the multi-site self-healing microcapsules and modified epoxy resin were chemically cross-linked with isocyanate and diamine via addition polymerization to prepare a self-healing polyurea-modified epoxy resin coating containing multi-site graphene oxide microcapsules.

[0043] The specific preparation steps are as follows:

[0044] Step 1, preparation of functional group-modified graphene oxide:

[0045] A certain amount of graphene oxide is mixed with isocyanate and functionalized under certain reaction conditions to obtain isocyanate-functionalized graphene oxide, namely isocyanate graphene oxide NCO-GO.

[0046] The isocyanate used in the preparation of NCO-GO is any one or more of isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), toluene diisocyanate (TDI), and xylene diisocyanate (MDI);

[0047] The specific operation is as follows: Graphene oxide is mixed with isocyanate at a ratio of 2.5wt% to 10wt%, nitrogen is used as a protective atmosphere during the reaction, the reaction temperature is 50-60°C, and the reaction time is 2-3h to obtain isocyanate group-functionalized graphene oxide (NCO-GO);

[0048] Step 2, prepare the water phase and the oil phase:

[0049] Weigh a certain amount of the modified graphene oxide prepared in step 1 into deionized water, heat it to a certain temperature, and fully stir and disperse it to obtain an aqueous phase;

[0050] Add isocyanate, diamine and repair agent into a beaker, stir and dissolve them under certain conditions to form a uniform phase to obtain an oil phase;

[0051] The stirring temperature of the aqueous phase is 25° C. to 50° C., and the content of NCO-GO is 1 wt% to 5 wt%; the isocyanate in the oil phase is one or more of isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), toluene diisocyanate (TDI), xylene diisocyanate (MDI), etc.; the diamine is one or more of diethylenetriamine (DETA), hexamethylenetetramine, ethylenediamine, triethylenediamine, and 1,6-hexanediamine; and the repair agent is one or more of epoxy resin, isocyanate, tung oil, and linseed oil;

[0052] A mixture of isocyanate and diamine is used as the shell material, and the ratio of the two is 1:1; the repair agent is used as the core material, and the ratio of the shell material to the core material is 2-3:1. The temperature of the oil phase when stirring and dissolving is 30°C-40°C;

[0053] Step 3, preparation of Pickering emulsion (O / W):

[0054] The aqueous phase and oil phase prepared in step 2 are stirred in a certain manner, stirring rate and stirring temperature to prepare a Pickering emulsion, and the pH value of the emulsion and the amount of modified NCO-GO added are adjusted to obtain an emulsion of appropriate size;

[0055] The parameters for preparing the Pickering emulsion are as follows: the ratio of the oil phase to the water phase is 1:3-9, the pH value of the solution during stirring is 2-5, the stirring method is one of magnetic stirring, stirring paddle, and homogenizer, the stirring rate is 1000-3000 rpm, and the stirring temperature is 25°C-40°C;

[0056] Step 4: Preparation of multi-site self-repairing microcapsules:

[0057] The Pickering emulsion obtained in step 3 is slowly stirred under certain pH and temperature conditions to initiate an in-situ polymerization reaction for a period of time to fully solidify the polyurea microcapsule shell. After the reaction period, a certain amount of the aqueous phase solution of the Pickering emulsion prepared in step 3 is added to graft NCO-GO onto the microcapsule surface. The fully reacted solution is then centrifuged, washed, and dried to obtain multi-site self-healing microcapsules.

[0058] The specific parameters are as follows: adjust the speed of the Pickering emulsion to 500-800 rpm, slowly raise the temperature to 60-70°C, adjust the pH to 2-5, and continue the reaction for 2-3 hours to fully solidify the shell material to obtain a microcapsule suspension. The aqueous phase solution prepared in step 3 is added to the microcapsule suspension. The mass of the added aqueous phase solution is 0.3-0.5 times that of the aqueous phase of the Pickering emulsion in step 3. Continue the reaction for 2-3 hours to complete the NCO-GO grafting. Subsequently, the centrifuged microcapsules are thoroughly washed with anhydrous ethanol, acetone, and deionized water. Finally, the obtained microcapsules are placed in a vacuum oven and vacuum-dried for 24-48 hours to obtain multi-site self-healing microcapsules.

[0059] Step 5: Preparation of flexible modified epoxy resin:

[0060] A certain amount of amino-terminated organosilicon is mixed with epoxy resin, added to a solvent, and group modified under certain temperature and reaction time conditions to obtain amino-terminated organosilicon-modified epoxy resin;

[0061] The epoxy resin added in the preparation of the silicone-modified epoxy resin is one or more of E-03, E-12, E-20, diaminodiphenylmethane tetraglycidylamine (TU13nnrr), diglycidyl p-aminophenol (TUY.AP), and 3-ESL aminomethylcyclohexane; the silicone is any one or more of amino-terminated polydimethylsiloxane, amino-terminated polydiethylsiloxane, and amino-terminated polymethylphenylsiloxane; and the solvent is any one or more of ethyl acetate, N,N-dimethylformamide (DMF), and anhydrous ethanol.

[0062] The specific parameters are as follows: the amino-terminated silicone and the epoxy resin are mixed in a ratio of 0.5 to 1:1, the amount of solvent added is 10 wt% to 20 wt%, the stirring method is magnetic stirring, the stirring rate is 300 to 500 rpm, the reaction temperature is 70°C to 80°C, and the reaction time is 3 hours to 6 hours; the fully reacted amino-terminated modified epoxy resin is fully dried in a vacuum drying oven to remove the solvent, thereby obtaining the amino-terminated modified epoxy resin;

[0063] Step 6: Prepare a multi-point interpenetrating cross-linked modified epoxy resin coating:

[0064] The multi-site self-healing microcapsules obtained in step 4 and the amino-terminated modified epoxy resin prepared in step 5 are reacted with isocyanate and diamine by addition polymerization under certain conditions in the presence of a catalyst to prepare a self-healing polyurea-modified epoxy resin coating with multi-site NCO-GO microcapsules;

[0065] The amino-terminated modified epoxy resin, isocyanate, and diamine are added in a ratio of 1 to 3:1:1; the isocyanate is any one or more of isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), toluene diisocyanate (TDI), and xylene diisocyanate (MDI); the diamine is any one or more of diethylenetriamine (DETA), hexamethylenetetramine, ethylenediamine, triethylenediamine, and 1,6-hexanediamine; the solvent is any one or more of ethyl acetate, N,N-dimethylformamide, and anhydrous ethanol; and the catalyst is dibutyltin dilaurate.

[0066] The specific operation is as follows: adding the prepared multi-site self-healing microcapsules to a polyurea-modified epoxy resin matrix at a ratio of 1.5wt% to 4.5wt%; adding terminal amino-modified epoxy resin, isocyanate and diamine as raw materials for the addition reaction, and adding 10wt% to 20wt% of solvent and 0.02wt% to 0.04wt% of catalyst, polymerizing for 3 to 6 hours at a reaction temperature of 70 to 80°C, stirring by magnetic stirring, and stirring at a rate of 300 to 500rpm; removing the solvent in the modified epoxy resin by drying in a vacuum drying oven, and finally curing at 70 to 80°C for 24 to 48 hours to obtain a multi-point interpenetrating cross-linked modified self-healing microcapsule epoxy resin coating.

[0067] The present invention modifies the functional groups of graphene oxide by adjusting the type of isocyanate to obtain modified NCO-GO with grafted active groups and good dispersibility; by regulating the addition content of different modified NCO-GO in the aqueous phase, the best emulsification effect is obtained, and the obtained Pickering emulsion has a uniform particle size; by adjusting different isocyanates in the oil phase as shell materials, the hydrogen bond content inside the microcapsule is increased, thereby obtaining more excellent self-healing performance; by introducing a repair agent into the core material, a synergistic effect is generated with the modified matrix after the shell material is damaged and released; by regulating the ratio of the oil phase to the aqueous phase in the range of 1:3 to 9, changing the pH value range to 2 to 5, controlling the stirring mode, and the stirring rate to 1000 to 3000 rpm and other parameters to control the size of the emulsion, finally obtaining an emulsion of 40 to 50 mm in size; by adjusting the stirring rate of the Pickering emulsion during the polymerization process to The speed is between 500 and 800 rpm to provide sufficient shear force without destroying the emulsion droplets. At the same time, the temperature is raised to 60 to 70°C for a full 2 ​​to 3 hours to allow the microcapsules to form shells more stably and solidify. NCO-GO is grafted onto the surface of the microcapsule shell by adding the aqueous phase in steps to obtain multi-site self-healing microcapsules coated with NCO-GO. The mechanical properties of the epoxy resin are modified by end-amino silicone, and active groups are provided for the epoxy resin to participate in the polyurea synthesis reaction. By modifying the groups of graphene oxide, it is chemically grafted to the outer layer of the microcapsule to increase the active sites in the polymerization reaction, improve the integrity of the coating, and thus enhance the mechanical properties of the matrix. By regulating the addition content of the multi-site self-healing microcapsules in the polyurea-modified epoxy matrix, it acts as a second phase reinforcement, forming a synergistic effect with the network cross-linked epoxy resin matrix after polyurea modification, thereby enhancing the mechanical properties and self-healing properties.

[0068] The present invention prepares a multi-point interpenetrating cross-linking self-healing polycapsule urea micro-modified epoxy coating by a step-by-step polymerization method. First, by adjusting the type of isocyanate, the isocyanate group is modified into graphene oxide NCO-GO, and the component is grafted onto the surface of the microcapsule as a surface modifier to obtain highly reactive microcapsules. Polyurea microcapsules are prepared by Pickering emulsification to improve the stability of the emulsion interface and the size controllability. NCO-GO is grafted onto the self-healing microcapsules by in-situ polymerization to form self-healing microcapsules with multiple points, providing surface active sites and improving the mechanical properties and integrity of the coating. By adjusting the types of isocyanate and diamine, the strength of the dynamic hydrogen bonds of the microcapsules is increased, so that the microcapsules have excellent self-healing properties. The use of amino-terminated silicone to modify epoxy coatings for toughening can effectively improve the brittleness of the substrate. The introduction of amino-reactive groups gives the epoxy matrix "chain-forming units" that form an interpenetrating, cross-linked urea bond molecular network, improving the mechanical properties of the coating while imparting dynamic self-repair capabilities to the epoxy matrix. This, combined with the multi-point self-repairing microcapsules, forms a "foreign aid + intrinsic" repair synergistic mechanism, enhancing self-repair performance. Furthermore, NCO-GO and microcapsules act as second-phase reinforcements in the coating, pinning them to damaged areas of the coating to achieve a synergistic reinforcement effect and improve the protective effect. This technology has broad application prospects in coating repair, extending coating life, enhancing mechanical properties, reducing epoxy resin brittleness, and improving protective effectiveness.

[0069] The technical solution of the present invention is further illustrated by the following examples.

[0070] Example 1

[0071] First, 2.5wt% of graphene oxide was weighed and mixed with 97.5wt% of isophorone diisocyanate (IPDI) and hexamethylene diisocyanate (HDI), wherein the ratio of isophorone diisocyanate (IPDI) to hexamethylene diisocyanate (HDI) was 1:1; nitrogen was introduced into a three-necked flask as a protective atmosphere, the reaction temperature was 60°C, and the reaction time was 3h to obtain isocyanate group-functionalized graphene oxide (NCO-GO).

[0072] 1wt% of functional group-modified graphene oxide was weighed and added to 99wt% of deionized water, and the mixture was fully stirred at 25°C to form a uniform phase as the water phase; 33.3wt% of isophorone diisocyanate (IPDI) and hexamethylene diisocyanate (HDI) and 33.3wt% of diethylenetriamine (DETA) were weighed, wherein the ratio of isophorone diisocyanate (IPDI) to hexamethylene diisocyanate (HDI) was 1:1; 33.3wt% of the repair agent epoxy resin was then added thereto, stirred and dissolved at 40°C, and a uniform phase was obtained after full dissolution, which was the oil phase.

[0073] The prepared aqueous phase and oil phase (3:1) were added into a beaker and stirred at 1000 rpm using a stirring paddle. The pH of the solution was controlled to be 2. The mixture was stirred at 40° C. to obtain a Pickering emulsion of appropriate size.

[0074] The Pickering emulsion was transferred to a three-necked flask, and the rotation speed was adjusted to 500-800 rpm. The temperature was slowly raised to 70°C, the pH of the solution was controlled at 2, and the reaction was continued for 2 hours to fully solidify the shell material to obtain a microcapsule suspension. The prepared aqueous solution was added to the microcapsule suspension. The mass of the added aqueous solution was 0.3 times that of the aqueous phase of the Pickering emulsion. The reaction was continued for 3 hours to complete the NCO-GO grafting. Subsequently, the centrifuged microcapsules were fully washed with anhydrous ethanol, acetone and deionized water. The centrifugal treatment parameters were: 7500 rpm, 5 min, repeated 3-4 times, and finally the obtained microcapsules were placed in a vacuum oven and vacuum dried for 24 hours to obtain multi-site self-healing microcapsules.

[0075] 90 wt% of amino-terminated polydimethylsiloxane (PDMS) and epoxy resin E-03 were weighed in a ratio of 1:1, and 10 wt% of DMF solvent was added to the flask. They were blended and fully reacted by magnetic stirring at a stirring rate of 300 rpm, a reaction temperature of 70°C, and a reaction time of 6 h. The amino-terminated modified epoxy resin after the reaction was vacuum dried in a vacuum drying oven for 48 h to obtain an amino-terminated modified epoxy resin.

[0076] 1.5wt% multi-site self-healing microcapsules, end-amino modified epoxy resin, isocyanate and diethylenetriamine (DETA) as raw materials for addition reaction were mixed and reacted by addition polymerization, wherein the isocyanate was isophorone diisocyanate (IPDI) and hexamethylene diisocyanate (HDI), and the addition ratio was 1:1; the addition ratios of end-amino modified epoxy resin, isocyanate and diethylenetriamine were 1:1:1 respectively; and 10wt% DMF was added as solvent and 0.02wt% dibutyltin dilaurate was added as catalyst. The polymerization was carried out at a reaction temperature of 70°C for 6h, the stirring method was magnetic stirring, and the stirring rate was 300rpm; the mixture was poured into a polytetrafluoroethylene mold, and the solvent in the modified epoxy resin was removed by drying at 70°C in a vacuum drying oven, and finally cured at 70°C for 48h to obtain a multi-point interpenetrating cross-linked modified self-healing microcapsule epoxy resin coating.

[0077] Example 2

[0078] First, 5wt% of graphene oxide was weighed and mixed with 95wt% of toluene diisocyanate (TDI) and xylene diisocyanate (MDI), with the ratio of toluene diisocyanate (TDI) to xylene diisocyanate (MDI) being 1:1; nitrogen was introduced into a three-necked flask as a protective atmosphere, the reaction temperature was 55°C, and the reaction time was 2.5h to obtain isocyanate group-functionalized graphene oxide (NCO-GO).

[0079] 3wt% of functional group-modified graphene oxide was weighed and added to 97wt% of deionized water, and the mixture was fully stirred at 35°C to form a uniform phase as the water phase; 35.7wt% of toluene diisocyanate (TDI) and xylene diisocyanate (MDI) and 35.7wt% of diethylenetriamine (DETA) were weighed, wherein the ratio of toluene diisocyanate (TDI) to xylene diisocyanate (MDI) was 1:1; then 28.6wt% of the repair agent epoxy resin was added thereto, stirred and dissolved at 35°C, and a uniform phase was obtained after full dissolution, which was the oil phase.

[0080] The prepared aqueous phase and oil phase (5:1) were added into a beaker and stirred at 2000 rpm using a stirring paddle. The pH of the solution was controlled to be 3 and the mixture was stirred at 30°C to obtain an emulsion of appropriate size.

[0081] The Pickering emulsion was transferred to a three-necked flask, and the rotation speed was adjusted to 500-800 rpm. The temperature was slowly raised to 65°C, the pH of the solution was controlled at 3, and the reaction was continued for 2.5 hours to fully solidify the shell material to obtain a microcapsule suspension. The prepared aqueous solution was added to the microcapsule suspension. The mass of the added aqueous solution was 0.4 times that of the aqueous phase of the Pickering emulsion. The reaction was continued for 2.5 hours to complete the NCO-GO grafting; then, the centrifuged microcapsules were thoroughly washed with anhydrous ethanol, acetone and deionized water. The centrifugation parameters were: 7500 rpm, 5 min, repeated 3-4 times, and finally the obtained microcapsules were placed in a vacuum oven and vacuum dried for 36 hours to obtain multi-site self-healing microcapsules.

[0082] 85 wt% of amino-terminated polydimethylsiloxane (PDMS) and epoxy resin E-03 were weighed in a ratio of 1:1, and 15 wt% of DMF solvent was added to a flask. They were blended and fully reacted by magnetic stirring at a stirring rate of 400 rpm, a reaction temperature of 75°C, and a reaction time of 4 h. The amino-terminated modified epoxy resin after the reaction was vacuum dried in a vacuum drying oven for 36 h to obtain an amino-terminated modified epoxy resin.

[0083] 3wt% of multi-site self-healing microcapsules, as well as amino-modified epoxy resin, isocyanate and diethylenetriamine (DETA) as raw materials for addition reaction were mixed and reacted by addition polymerization, wherein the isocyanate was toluene diisocyanate (TDI) and xylene diisocyanate (MDI), and the addition ratio was 1:1; the amino-modified epoxy resin, isocyanate and diethylenetriamine were added in a ratio of 2:1:1 respectively; and 15wt% of DMF was added as solvent and 0.03wt% of dibutyltin dilaurate was added as catalyst. The polymerization was carried out at a reaction temperature of 75°C for 4h, the stirring method was magnetic stirring, and the stirring rate was 400rpm; the mixture was poured into a polytetrafluoroethylene mold, and the solvent in the modified epoxy resin was removed by drying in a vacuum drying oven at 75°C, and finally cured at 75°C for 36h to obtain a multi-point interpenetrating cross-linked modified self-healing microcapsule epoxy resin coating.

[0084] Example 3

[0085] First, 7.5wt% of graphene oxide was weighed and mixed with 92.5wt% of isophorone diisocyanate (IPDI) and hexamethylene diisocyanate (HDI), wherein the ratio of isophorone diisocyanate (IPDI) to hexamethylene diisocyanate (HDI) was 1:1; nitrogen was introduced into a three-necked flask as a protective atmosphere, the reaction temperature was 55°C, and the reaction time was 3h to obtain isocyanate group-functionalized graphene oxide (NCO-GO).

[0086] 2wt% of functional group-modified graphene oxide was weighed and added to 98wt% of deionized water, and the mixture was fully stirred at 40°C to form a uniform phase as the water phase; 50wt% of isophorone diisocyanate (IPDI) and hexamethylene diisocyanate (HDI) and 25wt% of ethylenediamine were weighed, wherein the ratio of isophorone diisocyanate (IPDI) to hexamethylene diisocyanate (HDI) was 1:1; then 25wt% of the repair agent isocyanate was added thereto, stirred and dissolved at 35°C, and a uniform phase was obtained after full dissolution, which was the oil phase.

[0087] The prepared aqueous phase and oil phase (7:1) were added into a beaker and stirred at 2000 rpm using a stirring paddle. The pH of the solution was controlled to be 4 and the mixture was stirred at 35°C to obtain an emulsion of appropriate size.

[0088] The Pickering emulsion was rotated at 600 rpm and slowly heated to 65°C. The pH of the solution was controlled at 4 and the reaction was continued for 2 hours to fully solidify the shell material to obtain a microcapsule suspension. The prepared aqueous solution was added to the microcapsule suspension. The mass of the added aqueous solution was 0.4 times that of the aqueous phase of the Pickering emulsion. The reaction was continued for 2 hours to complete the NCO-GO grafting. Subsequently, the centrifuged microcapsules were thoroughly washed with anhydrous ethanol, acetone and deionized water. The centrifugation parameters were: 7500 rpm, 5 min, repeated 3 to 4 times, and finally the obtained microcapsules were placed in a vacuum oven and vacuum dried for 36 hours to obtain multi-site self-healing microcapsules.

[0089] 85 wt% of amino-terminated polydiethylsiloxane and epoxy resin E-12 were weighed in a ratio of 0.7:1, and 15 wt% of DMF solvent was added to a flask. They were blended and magnetically stirred at a stirring rate of 400 rpm, a reaction temperature of 75°C, and a reaction time of 4 h for full reaction. The amino-terminated modified epoxy resin after the reaction was vacuum dried in a vacuum drying oven for 36 h to obtain an amino-terminated modified epoxy resin.

[0090] 3wt% of multi-site self-healing microcapsules, end-amino modified epoxy resin, isocyanate and ethylenediamine were mixed as raw materials for addition reaction by addition polymerization, wherein the isocyanate was isophorone diisocyanate (IPDI) and hexamethylene diisocyanate (HDI), and the addition ratio was 1:1; the addition ratios of end-amino modified epoxy resin, isocyanate and ethylenediamine were 2:1:1 respectively; 15wt% of DMF was added as solvent and 0.03wt% of dibutyltin dilaurate was added as catalyst. The polymerization was carried out at a reaction temperature of 75°C for 4h, the stirring method was magnetic stirring, and the stirring rate was 400rpm; the mixture was poured into a polytetrafluoroethylene mold, and the solvent in the modified epoxy resin was removed by drying in a vacuum drying oven at 75°C, and finally cured at 75°C for 36h to obtain a multi-point interpenetrating cross-linked modified self-healing microcapsule epoxy resin coating.

[0091] Example 4

[0092] First, 10 wt% of graphene oxide was weighed and mixed with 90 wt% of isophorone diisocyanate (IPDI) and xylene diisocyanate (MDI), wherein the ratio of isophorone diisocyanate (IPDI) to xylene diisocyanate (MDI) was 1:1; nitrogen was introduced into a three-necked flask as a protective atmosphere, the reaction temperature was 50°C, and the reaction time was 2 h to obtain isocyanate group-functionalized graphene oxide (NCO-GO).

[0093] 5wt% of functional group-modified graphene oxide was weighed and added to 95wt% of deionized water, and fully stirred at 50°C to form a homogeneous phase as the water phase; 25wt% of isophorone diisocyanate (IPDI), 50wt% of xylene diisocyanate (MDI), and 25wt% of diethylenetriamine (DETA) were weighed, and then 25wt% of the repair agent tung oil was added thereto, stirred and dissolved at 30°C, and a homogeneous phase was obtained after full dissolution, which was the oil phase.

[0094] The prepared water phase and oil phase (9:1) were added into a beaker and stirred at 3000 rpm using a stirring paddle. The pH of the solution was controlled to be 5 and the mixture was stirred at 25°C to obtain an emulsion of appropriate size.

[0095] The Pickering emulsion was transferred to 800 rpm and slowly heated to 60°C. The pH of the solution was controlled at 5 and the reaction was continued for 2 hours to fully solidify the shell material to obtain a microcapsule suspension. The prepared aqueous solution was added to the microcapsule suspension. The mass of the added aqueous solution was 0.5 times that of the aqueous phase of the Pickering emulsion. The reaction was continued for 2 hours to complete the NCO-GO grafting. Subsequently, the centrifuged microcapsules were thoroughly washed with anhydrous ethanol, acetone and deionized water. The centrifugation parameters were: 7500 rpm, 5 min, repeated 3 to 4 times, and finally the obtained microcapsules were placed in a vacuum oven and vacuum dried for 24 hours to obtain multi-site self-healing microcapsules.

[0096] 80 wt% of amino-terminated polymethylphenylsiloxane and epoxy resin E-20 were weighed in a ratio of 0.5:1, and 20 wt% of DMF solvent was added to a flask. They were blended and fully reacted by magnetic stirring at a stirring rate of 500 rpm, a reaction temperature of 80°C, and a reaction time of 3 h. The amino-terminated modified epoxy resin after the reaction was vacuum dried in a vacuum drying oven for 24 h to obtain an amino-terminated modified epoxy resin.

[0097] 4.5wt% of multi-site self-healing microcapsules, end-amino modified epoxy resin, isocyanate and ethylenediamine were mixed as raw materials for addition reaction by addition polymerization, wherein the isocyanate was isophorone diisocyanate (IPDI) and xylene diisocyanate (MDI), and the addition ratio was 1:1; the addition ratios of end-amino modified epoxy resin, isocyanate and ethylenediamine were 3:1:1 respectively; 20wt% of DMF was added as solvent and 0.04wt% of dibutyltin dilaurate was added as catalyst. The polymerization was carried out at a reaction temperature of 80°C for 3h, the stirring method was magnetic stirring, and the stirring rate was 500rpm; the mixture was poured into a polytetrafluoroethylene mold, and the solvent in the modified epoxy resin was removed by drying in a vacuum drying oven at 80°C, and finally cured at 80°C for 24h to obtain a multi-point interpenetrating cross-linked modified self-healing microcapsule epoxy resin coating.

[0098] Table 1 compares the fracture strength and self-healing efficiency of the multi-point interpenetrating cross-linked self-healing microcapsule polyurea-modified epoxy resin coating, the self-healing coating with loaded PU / PANI microcapsules, and the conventional epoxy coating in Example 1. As can be seen from Table 1, the conventional epoxy coating has a higher fracture strength, but the toughness of the matrix itself is poor, and the matrix itself does not have a self-healing function. Although the self-healing coating with loaded PU / PANI microcapsules has good self-healing efficiency and elongation at break, its fracture strength is lower than that of the conventional epoxy matrix because the epoxy matrix itself is not tightly bonded to the microcapsules, and the overall mechanical properties of the coating are relatively low. The multi-point interpenetrating cross-linking self-repairing microcapsule polyurea modified epoxy resin coating in Example 1 adopts an epoxy matrix and is modified using a polyurea molecular network structure. At the same time, multi-site microcapsules are introduced as active sites for the polymerization reaction to increase the cross-linking density. The microcapsules can also serve as second-phase reinforcements to improve the mechanical properties of the coating. The polyurea microcapsules with the core material as the repair agent can form a synergistic effect with the dynamic hydrogen bonds in the polyurea modified epoxy matrix. Therefore, the self-repairing efficiency and mechanical properties of the multi-point interpenetrating cross-linking self-repairing microcapsule polyurea modified epoxy resin coating in Example 1 are higher than those of the self-repairing coating of PU / PANI microcapsules.

[0099] Table 1 Fracture strength, self-repairing efficiency and elongation at break of multi-point interpenetrating cross-linked self-repairing microcapsule polyurea modified epoxy resin coating, PU / PANI microcapsule self-repairing coating and conventional epoxy coating in Example 1

[0100]

[0101] Figure 1 This is a schematic diagram of the cross-sectional morphology of the multi-point interpenetrating cross-linked self-repairing microcapsule polyurea modified epoxy resin coating prepared by the present invention. Figure 1It can be seen that the cured polyurea molecular network and multi-site self-healing microcapsules can be tightly combined with the epoxy matrix. At the same time, the microcapsules inside the matrix can be evenly distributed, providing multiple reactive sites, which can achieve synergistic repair with the matrix after damage.

Claims

1. A method for preparing a multi-point interpenetrating cross-linked self-repairing polyurea microcapsule modified epoxy coating, characterized in that: Graphene oxide is modified by isocyanate groups to obtain isocyanate graphene oxide NCO-GO. NCO-GO is used as the aqueous phase to prepare a Pickering emulsion with the oil phase formed by isocyanate, diamine and repair agent. The polyurea microcapsule shell in the emulsion is fully cured by initiating in situ polymerization. After a period of reaction, the prepared aqueous phase solution of the Pickering emulsion is added to graft NCO-GO onto the surface of the microcapsules, and the epoxy resin is modified with terminal amino silicone to make it flexible. Finally, the multi-site self-healing microcapsules and modified epoxy resin are chemically cross-linked with isocyanate and diamine by addition polymerization to prepare a self-healing polyurea-modified epoxy resin coating with multi-site graphene oxide microcapsules.

2. The method for preparing a multi-point interpenetrating cross-linked self-repairing polyurea microcapsule modified epoxy coating according to claim 1, characterized in that: Please follow the steps below to implement: Step 1, preparation of functional group-modified graphene oxide: A certain amount of graphene oxide is mixed with isocyanate and functionalized under certain reaction conditions to obtain isocyanate-functionalized graphene oxide, namely isocyanate graphene oxide NCO-GO. Step 2, prepare the water phase and the oil phase: Weigh a certain amount of NCO-GO prepared in step 1 into deionized water, heat it to a certain temperature, and stir and disperse it thoroughly to obtain an aqueous phase; Add isocyanate, diamine and repair agent into a beaker, stir and dissolve them under certain conditions to form a uniform phase to obtain an oil phase; Step 3, prepare Pickering emulsion: The aqueous phase and the oil phase prepared in step 2 are stirred in a certain manner, at a certain stirring rate and at a certain stirring temperature to prepare a Pickering emulsion, and the pH value of the emulsion and the amount of NCO-GO added are adjusted to obtain an emulsion; Step 4: Preparation of multi-site self-repairing microcapsules: The Pickering emulsion obtained in step 3 is slowly stirred under certain pH and temperature conditions to initiate an in-situ polymerization reaction for a period of time to fully solidify the polyurea microcapsule shell. After the reaction period, a certain amount of the aqueous phase solution of the Pickering emulsion prepared in step 3 is added to graft NCO-GO onto the microcapsule surface. The fully reacted solution is then centrifuged, washed, and dried to obtain multi-site self-healing microcapsules. Step 5: Preparation of flexible modified epoxy resin: A certain amount of amino-terminated organosilicon is mixed with epoxy resin, added to a solvent, and group modified under certain temperature and reaction time conditions to obtain an amino-terminated organosilicon-modified epoxy resin; Step 6: Prepare a multi-point interpenetrating cross-linked modified epoxy resin coating: The multi-site self-healing microcapsules obtained in step 4 and the amino-terminated modified epoxy resin prepared in step 5 are reacted with isocyanate and diamine by addition polymerization under certain conditions in the presence of a catalyst to prepare a self-healing polyurea-modified epoxy resin coating with multi-site NCO-GO microcapsules.

3. The method for preparing a multi-point interpenetrating cross-linked self-repairing polyurea microcapsule modified epoxy coating according to claim 2, characterized in that: The isocyanate in step 1 is any one or more of isophorone diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, and xylene diisocyanate.

4. The method for preparing a multi-point interpenetrating cross-linked self-repairing polyurea microcapsule modified epoxy coating according to claim 2, characterized in that: In step 1, graphene oxide is mixed with isocyanate at a ratio of 2.5 wt% to 10 wt%, nitrogen is used as a protective atmosphere during the reaction, the reaction temperature is 50 to 60 ° C, and the reaction time is 2 to 3 hours to obtain isocyanate-terminated graphene oxide NCO-GO.

5. The method for preparing a multi-point interpenetrating cross-linked self-repairing polyurea microcapsule modified epoxy coating according to claim 2, characterized in that: The stirring temperature of the aqueous phase in step 2 is 25° C. to 50° C., and the content of graphene oxide NCO-GO is 1 wt % to 5 wt %.

6. The method for preparing a multi-point interpenetrating cross-linked self-repairing polyurea microcapsule modified epoxy coating according to claim 2, characterized in that: In step 2, the isocyanate in the oil phase is any one or more of isophorone diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, and xylene diisocyanate; the diamine is any one or more of diethylenetriamine, hexamethylenetetramine, ethylenediamine, triethylenediamine, and 1,6-hexanediamine; the repair agent is any one or more of epoxy resin, isocyanate, tung oil, and linseed oil; a mixture of isocyanate and diamine is used as the shell material, and the addition ratio of the two is 1:1; the repair agent is used as the core material, and the ratio of the shell material to the core material is 2 to 3:

1. The temperature when the oil phase is stirred and dissolved is 30°C to 40°C.

7. The method for preparing a multi-point interpenetrating cross-linked self-repairing polyurea microcapsule modified epoxy coating according to claim 2, characterized in that: The parameters for preparing the Pickering emulsion in step 3 are: the ratio of the oil phase to the water phase is 1:3-9, the pH value of the solution during stirring is 2-5, the stirring method is any one of magnetic stirring, stirring paddle, and homogenizer, the stirring rate is 1000-3000 rpm, and the stirring temperature is 25°C-40°C.

8. The method for preparing a multi-point interpenetrating cross-linked self-repairing polyurea microcapsule modified epoxy coating according to claim 2, characterized in that: The specific operation for preparing the multi-site self-healing microcapsules in step 4 is as follows: adjusting the speed of the Pickering emulsion to 500-800 rpm, slowly raising the temperature to 60-70°C, adjusting the pH value to 2-5, and continuing the reaction for 2-3 hours to fully solidify the shell material to obtain a microcapsule suspension; adding the aqueous solution prepared in step 3 to the microcapsule suspension, the mass of the added aqueous solution being 0.3-0.5 times the aqueous phase of the Pickering emulsion prepared in step 3, and continuing the reaction for 2-3 hours to complete the NCO-GO grafting; then, thoroughly washing the centrifuged microcapsules with anhydrous ethanol, acetone, and deionized water, and finally placing the obtained microcapsules in a vacuum oven for vacuum drying for 24-48 hours to obtain multi-site self-healing microcapsules.

9. The method for preparing a multi-point interpenetrating cross-linked self-repairing polyurea microcapsule modified epoxy coating according to claim 2, characterized in that: In step 5, the epoxy resin is any one or more of E-03, E-12, E-20, diaminodiphenylmethane tetraglycidylamine, diglycidyl p-aminophenol, and 3-ESL aminomethylcyclohexane; the organosilicon is any one or more of amino-terminated polydimethylsiloxane, amino-terminated polydiethylsiloxane, and amino-terminated polymethylphenylsiloxane; and the solvent is any one or more of ethyl acetate, N,N-dimethylformamide, and anhydrous ethanol; The specific parameters are as follows: the amino-terminated silicone and the epoxy resin are mixed in a ratio of 0.5 to 1:1, the amount of solvent added is 10 wt% to 20 wt%, the stirring method is magnetic stirring, the stirring rate is 300 to 500 rpm, the reaction temperature is 70°C to 80°C, and the reaction time is 3 hours to 6 hours; the fully reacted amino-terminated modified epoxy resin is fully dried in a vacuum drying oven to remove the solvent to obtain the amino-terminated modified epoxy resin.

10. The method for preparing a multi-point interpenetrating cross-linked self-repairing polyurea microcapsule modified epoxy coating according to claim 2, characterized in that: When preparing the multi-point interpenetrating cross-linked modified epoxy resin coating in step 6, the addition ratio of the amino-terminated modified epoxy resin, isocyanate and diamine is 1-3:1:1, the isocyanate is any one or more of isophorone diisocyanate, hexamethylene diisocyanate, toluene diisocyanate and xylene diisocyanate; the diamine is any one or more of diethylenetriamine, hexamethylenetetramine, ethylenediamine, triethylenediamine and 1,6-hexanediamine; the solvent is any one or more of ethyl acetate, N,N-dimethylformyl and anhydrous ethanol; and the catalyst is dibutyltin dilaurate; The specific operation is as follows: the prepared multi-site self-repairing microcapsules are added into the polyurea-modified epoxy resin matrix at a ratio of 1.5wt% to 4.5wt%; End-amino-modified epoxy resin, isocyanate and diamine are added as raw materials for the addition reaction, and 10wt%~20wt% of solvent and 0.02wt%~0.04wt% of catalyst are added. The polymerization is carried out at a reaction temperature of 70~80°C for 3~6 hours, and the stirring method is magnetic stirring at a stirring rate of 300~500rpm. The solvent in the modified epoxy resin is removed by drying in a vacuum drying oven, and finally the resin is cured at 70~80°C for 24~48 hours to obtain a multi-point interpenetrating cross-linked modified self-healing microcapsule epoxy resin coating.

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