Preparation method of polyurea modified polysiloxane anticorrosive coating

Abstract

This invention proposes a method for preparing a polyurea-modified polysiloxane anticorrosive coating, belonging to the field of polymer science. The invention consists of two components, A and B. Component A comprises a disulfide / silane dual-modified PAE resin, a reactive silane coupling agent, and a catalyst; component B is a single-hydroxyl-terminated silicone oil-modified HDI trimer. This invention utilizes the side-chain silanes for initial moisture tolerance and adhesion enhancement through synergistic modification of the two components, achieves later-stage surface hydrophobic transitions through thermodynamic driving, and imparts dynamic self-healing capabilities to the coating by combining the main chain disulfide bonds. This invention constructs a high-density organic-inorganic interpenetrating network, exhibiting excellent impermeability, hardness, and long-term stability.

Description

Technical Field

[0001] This invention belongs to the field of polymers, and particularly relates to a method for preparing a polyurea-modified polysiloxane anticorrosive coating. Background Technology

[0002] Polyurea coatings, as a novel solvent-free and pollution-free spray coating technology following polyurethane, have been widely used in heavy-duty anti-corrosion, waterproofing, and industrial flooring projects due to their excellent mechanical properties, superior abrasion resistance, and rapid curing characteristics. Traditional polyurea coatings are mainly formed by the reaction of isocyanate components (usually isocyanate prepolymers) and amino compound components (usually polyetheramines and chain extenders). Because of their extremely high reactivity, they can complete cross-linking and film formation within seconds and are less affected by ambient temperature, thus holding an irreplaceable position in modern protective engineering.

[0003] In actual service and under complex construction environments, traditional polyurea coatings have revealed some significant technical defects. The isocyanate groups in the polyurea system have extremely strong electrophilic properties, making them highly susceptible to side reactions with trace amounts of moisture in the environment. In high-humidity construction sites or on metal substrates containing trace amounts of condensation, the reaction between isocyanate and water produces carbon dioxide gas. Because polyurea cures extremely quickly, air bubbles often cannot escape and are trapped inside the paint film or at the interface, leading to defects such as pinholes, craters, and porosity in the coating. This not only severely damages the integrity of the coating but also causes a precipitous drop in interfacial adhesion strength, becoming a major cause of subsequent coating blistering and peeling failure.

[0004] The surface protection function of polyurea coatings has limitations. Although ordinary polyurea coatings are dense, their surface energy is relatively high, making them highly susceptible to the adhesion of contaminants and the spread of moisture. During long-term service in marine or high-humidity / heat environments, corrosive media (such as chloride ions, oxygen, and water molecules) can slowly penetrate through the microscopic gaps between the polyurea molecular chains. While the industry often attempts to improve the hydrophobicity of coatings by physically adding low-surface-energy components such as organosilicon and fluorocarbons, these physical additives have poor compatibility with the polyurea matrix and are prone to surface precipitation or loss with the medium during long-term aging, leading to rapid degradation of the coating's surface performance and failing to achieve long-term, stable superhydrophobic protection.

[0005] Currently, existing technologies attempting to address these problems often suffer from trade-offs. For example, the introduction of high-molecular-weight inactive components to improve hydrophobicity often significantly reduces the hardness and mechanical strength of the paint film; chemical additives added to improve moisture tolerance may lead to uncontrolled curing rates. How to achieve a balance between these effects has become a critical issue that urgently needs to be addressed in the field of anti-corrosion coatings. Summary of the Invention

[0006] The first objective of this invention is to provide a polyurea-modified polysiloxane anticorrosive coating, comprising the following components by weight: Component A: Disulfide bond / silane dual-modified PAE resin 100 Reactive silane coupling agent 1.5-3.0 Catalyst 0.1-0.5 Component B: Single-hydroxyl-terminated silicone oil modified HDI trimer 45-55 The disulfide bond / silane dual-modified PAE resin is a hybrid resin formed by the addition reaction of polyaspartic acid ester, diisocyanate and diamine containing disulfide bonds to form a main chain containing urea bonds and disulfide bonds, and the addition of residual isocyanate groups on the side chain with aminoalkoxysilane to construct siloxane branches. The single-hydroxyl-terminated silicone oil modified HDI trimer is a prepolymer containing active isocyanate groups formed by the addition reaction of HDI trimer and single-hydroxyl-terminated polydimethylsiloxane, in which the siloxane segments are chemically anchored to the isocyanate backbone through urethane bonds.

[0007] Preferably, component B further contains 5-15 parts of a dehydrating diluent.

[0008] Preferably, component A further contains 10-25 parts of filler and 5-15 parts of pigment; the filler is a component that increases the thickness and hardness of the paint film; and the pigment is a component that provides hiding power and color matching.

[0009] Preferably, component A further contains 0.2-0.5 parts of a nonionic defoamer; 0.3-0.8 parts of a leveling agent; and 0.5-1.2 parts of a light stabilizer.

[0010] Preferably, the preparation steps of the disulfide bond / silane dual-modified PAE resin include: S1, Place the polyaspartic acid ester resin into the reaction vessel and perform dehydration pretreatment; S2, Inert gas is introduced into the reaction vessel, and aliphatic diisocyanate is added to carry out a bridging reaction; S3, a diamine containing a disulfide bond is added to the system to carry out a dynamic bond intercalation reaction; S4, add aminoalkoxysilane to the system, keep the reaction at a constant temperature; add organic solvent to adjust the solid content, and filter out the material.

[0011] The mass ratio of the polyaspartic ester resin, aliphatic diisocyanate, diamine containing disulfide bonds, aminoalkoxysilane, and organic solvent is 100:8-18:3-10:2-12:20-50.

[0012] Preferably, the preparation steps of the single-hydroxyl-terminated silicone oil modified HDI trimer include: S1, add HDI trimer and organic solvent to the reaction vessel, and introduce inert gas; S2, add the esterification catalyst to the reaction vessel and stir until homogeneous; S3, add single-hydroxyl-terminated silicone oil to the reaction vessel for grafting reaction, and then heat to ripen; S4, after maturation, is cooled and discharged.

[0013] The mass ratio of the HDI trimer, single-hydroxyl-terminated silicone oil, urethane catalyst, and organic solvent is 100:3-15:0.01-0.08:5-20; the number average molecular weight of the single-hydroxyl-terminated silicone oil is between 1000 and 5000.

[0014] Preferably, the mixing ratio of component A to component B is 1.05-1.10:1, calculated as the NCO / NH molar ratio.

[0015] A second objective of this invention is to provide a method for preparing the aforementioned polyurea-modified polysiloxane anticorrosive coating, the method comprising the following steps: (1) Preparation of component A: Take the disulfide bond / silane dual-modified PAE resin, add reactive silane coupling agent, catalyst and other components in sequence, disperse or grind at high speed to fineness ≤40μm to obtain uniform component A; (2) Preparation of component B: Take the single-hydroxyl-terminated silicone oil modified HDI trimer, add a dehydrating diluent as needed, and mix evenly to obtain component B; (3) Coating molding: Before use, the A component and the B component are mixed and stirred evenly to obtain the polyurea modified polysiloxane anti-corrosion coating.

[0016] This invention is based on the dynamic chemical evolution mechanism formed by the modification of the molecular structure of components A and B. Through the spatial arrangement of functional groups and the control of reaction kinetics, the coating can realize the surface energy transition and dynamic repair of chemical bonds from the initial interfacial wetting in the early stage of film formation to the later stage of curing.

[0017] In the early stages of film formation, the moisture tolerance mechanism of the system originates from the alkoxysilane side chains grafted in component A. Due to the specific polarity and hydrolytic activity of alkoxysilanes before complete condensation, they can synergistically work with reactive silane coupling agents during the application stage to actively consume trace amounts of moisture on the substrate surface for in-situ hydrolysis. This process competitively inhibits the side reaction between isocyanate groups and moisture to produce carbon dioxide, thus preventing the formation of bubbles and micropores within the paint film. Simultaneously, the silanol groups generated by hydrolysis can form covalent bonds with hydroxyl groups or other polar sites on the substrate surface, transforming moisture at the interface, which is originally unfavorable for adhesion, into components that build the Si-O-Si hybrid network, enhancing the chemical anchoring force of the coating on damp substrates.

[0018] The later hydrophobic transition effect originates from the self-stratification kinetics formed by the synergistic modification of components A and B. During the curing process, component A forms a polar skeleton with high crosslinking density through polyurea reaction and silane condensation. At this time, due to the extremely low surface energy of the single-terminated hydroxyl silicone oil segments in component B anchored by urethane bonds, the long siloxane chains spontaneously migrate towards the air interface under thermodynamic drive due to the repulsion effect of the polar network inside the system. The necessity of this distribution modification is that if component A is modified alone, the high proportion of silane grafting will significantly increase the resin viscosity and reduce its compatibility with isocyanate, and the steric hindrance of a single component restricts the free migration of siloxane segments; while the simultaneous modification of components A and B allows component B to act as a carrier for hydrophobic segments, ensuring good initial wettability in the early stage of mixing, and in the later stage of curing, the extrusion effect of the skeleton of component A achieves the ultimate enrichment of silicon segments on the surface, thereby causing a stepwise increase in the contact angle.

[0019] The self-healing mechanism is achieved through dynamic disulfide bonds nested within the main chain of component A. When the coating fractures under stress, the disulfide bonds on the fracture surface undergo a reversible dynamic exchange reaction under specific conditions. This invention maintains an appropriate proportion of flexible chain segments and molecular chain slip space within the system by precisely limiting the NCO / NH molar ratio to 1.05-1.10:1, providing kinetic support for the cross-interfacial recombination of disulfide bonds. This repair mechanism based on intra-chain dynamic covalent bonds, combined with the hydrophobic shielding layer provided by the side chains and curing agent, enables the coating to rebuild the chemical barrier while restoring its physical morphology, achieving a balance between structure and protective function.

[0020] The present invention has the following beneficial effects: (1) Achieving interfacial moisture absorption and adhesion enhancement: Through the synergistic effect of the side chain silane of component A and the reactive silane coupling agent, the trace amount of moisture at the interface is transformed into raw materials for constructing the Si-O-Si network, which solves the bottleneck of polyurea coatings being prone to foaming and having poor adhesion on damp substrates.

[0021] (2) It has a self-layered hydrophobic transition function: by utilizing the polarity difference and thermodynamic repulsion generated by the modification of the two components A and B, the siloxane segments are driven to migrate to the surface in a directional manner, so that the contact angle of the coating can be increased stepwise from the initial wetting to the later superhydrophobic in the later stage of curing.

[0022] (3) Balancing dynamic self-repair and barrier stability: The disulfide bonds nested in the main chain provide the ability to reorganize the molecular chain after damage. Combined with the chemically anchored rather than physically added siloxane segments, it ensures that the protective components are not lost or precipitated during the self-repair process.

[0023] (4) A high-performance organic-inorganic interpenetrating network (IPN) was constructed: through two-component synergistic modification, a hybrid structure with high cross-linking density was formed at the molecular scale, which significantly improved the pencil hardness, cohesive strength and long-term anti-permeation performance of the coating to electrolyte media. Attached Figure Description

[0024] Figure 1 The image shows the FT-IR spectrum of the uncrosslinked polyaspartic ester oligomer before modification.

[0025] Figure 2 The images show the FT-IR spectra of the modified PAE resin oligomers that have not yet undergone crosslinking of disulfide bonds / silane dual modification.

[0026] Figure 3 The FT-IR spectrum of HDI trimer modified with single-hydroxyl silicone oil is shown. Detailed Implementation

[0027] To better understand the present invention, the present invention will be further described below with reference to specific serial numbers. The terminology used in the serial numbers is for describing specific embodiments and does not constitute a limitation on the scope of protection of the present invention.

[0028] In the specific implementation methods, unless otherwise specified, the experimental methods used are all conventional methods, and the materials and reagents used are all commercially available unless otherwise specified.

[0029] Unless otherwise specified, percentages, % and so on in the specific implementation method are assumed to be mass percentages.

[0030] The polyaspartic acid ester (PAE) used in this invention is an uncured secondary amine oligomer with an average ammonia value of 195 mg KOH / g, an average equivalent mass of 287.3 g / eq, an average number-average molecular weight (Mn) of 800, a water content of 0.03 wt%, and a dynamic viscosity of 1200 mPa·s at 25°C.

[0031] The HDI trimer used in this invention is Desmodur N3300, with an average functionality of 3.2; a mass fraction of isocyanate groups (-NCO) of 21.8%; an average mass fraction of free HDI monomers of 0.2%; and a dynamic viscosity of 2500 mPa·s at 25°C.

[0032] The single-hydroxyl-terminated polydimethylsiloxane used in this invention has an average single-terminal functionalization rate of 99%, an average number-average molecular weight (Mn) of 2000, an average volatile content (low molecular weight cyclic) of 0.5 wt%, and a dynamic viscosity of 50 mPa·s at 25°C.

[0033] The aliphatic diisocyanate used in this invention is isophorone diisocyanate (IPDI), with a purity of 99.8%; the theoretical mass fraction of isocyanate group (-NCO) is 37.8%; and the average acid value is 0.01 mg KOH / g.

[0034] The diamine containing disulfide bonds used in this invention is 2,2'-diaminodiphenyl disulfide (DAPDS), with an average purity of 99.0% and an average moisture content of 0.05 wt%.

[0035] The organic solvent used in this invention is dehydrated grade butyl acetate with a purity of 99.8% and an average water content (Karl Fischer method) of 120 ppm. The solvent has undergone deep dehydration treatment with molecular sieves and is free of free alcohol and acidic impurities.

[0036] The reactive silane coupling agent used in this invention is an epoxy silane coupling agent (model: KH-560), whose chemical name is 3-glycidyl etheroxypropyltrimethoxysilane.

[0037] The catalyst used in this invention is an organometallic catalyst (model: dibutyltin dilaurate, DBTDL), with a tin content of 18.0%-19.0%.

[0038] The dehydrating diluent used in this invention is p-toluenesulfonyl isocyanate (model: TI), with an isocyanate group (-NCO) mass fraction of approximately 17.0%.

[0039] The filler used in this invention is ultrafine barium sulfate, with an average particle size (d50) of 0.5-1.0 μm.

[0040] The pigment used in this invention is rutile titanium dioxide, the surface of which is treated with an inorganic coating of silicon and aluminum.

[0041] The nonionic defoaming agent used in this invention is a defoaming polymer defoaming agent (model: BYK-066N).

[0042] The leveling agent used in this invention is a polyether-modified polydimethylsiloxane leveling agent (model: BYK-333).

[0043] The light stabilizer used in this invention is a hindered amine light stabilizer (model: Tinuvin292), whose chemical name is bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate.

[0044] Example 1: Preparation of low-proportion dual-modified PAE resin, including the following steps: (1) Material preparation: Prepare the following raw materials by weight: Polyaspartic acid ester (PAE) prepolymer: 100 parts; Isophorone diisocyanate (IPDI): 8 parts; 2,2'-Diaminodiphenyl disulfide (DAPDS): 3 parts; 3-Glycidyl etheroxypropyltrimethoxysilane (KH-560): 2 parts; Dehydrated grade butyl acetate: 20 parts.

[0045] (2) Specific preparation steps: S1 Pre-dehydration: Add 100 parts of PAE prepolymer to a four-necked reactor equipped with a stirrer, condenser and thermometer. Turn on the vacuum pump and dehydrate and stir for 2 hours at a temperature of 105℃ and a vacuum degree of -0.0095Mpa, then cool the material to 50℃.

[0046] S2 Bridging Reaction: High-purity nitrogen gas is introduced into the reactor for protection, maintaining the temperature at 50°C. IPDI monomer is added all at once. The reaction is stirred for 45 minutes to allow one of the isocyanate groups of IPDI to complete the addition reaction with the secondary amino group of PAE.

[0047] S3 dynamic bond insertion: DAPDS was dissolved in half the volume of butyl acetate and slowly added dropwise to the reactor. After the addition was complete, the temperature was raised to 75°C and the reaction was carried out for 3 hours. During this period, the -NCO content in the system was measured by sampling. The heating was stopped when the content reached the theoretical design value (indicating that the disulfide monomer had been inserted into the main chain through the urea bond).

[0048] S4 Side Branching: Adjust the reactor temperature to 60℃ and slowly add KH-560. After addition, raise the temperature again to 80℃ and maintain the reaction for 3 hours. The epoxy groups of KH-560 undergo a ring-opening reaction with the residual secondary amines on the chain segment, thereby constructing siloxane branches on the side of the polyurea backbone.

[0049] S5 Finished Product Processing: After the reaction is complete, the remaining butyl acetate is added to adjust the solid content, stirred evenly, and cooled to room temperature. The product is then filtered through a 200-mesh filter to obtain liquid disulfide / silane dual-modified PAE resin.

[0050] like Figure 1 The image shows the FT-IR spectrum of the PAE prepolymer before modification. Figure 2 This is the FT-IR spectrum of the finished product in this embodiment; it can be seen that after modification, PAE at 2270 cm⁻¹... -1 No obvious -NCO characteristic peaks were observed nearby, proving that the isocyanate used for bridging had reacted completely and the functional monomers had successfully achieved chemical bonding; in the fingerprint region, 1500 -1 The dense cluster of characteristic absorption peaks appearing within the range not only covers 1100 cm⁻¹ -1 The nearby Si-O-Si and Si-OC symmetric and asymmetric stretching vibrations introduced by silane grafting also include CS bonds (600-700 cm⁻¹) introduced after disulfide bonds are inserted into the main chain. -1 ) and various out-of-plane bending vibration signals that replace the benzene ring skeleton; these newly formed hybrid peaks and Figure 1 The comparison of a single PAE backbone signal confirmed that the multifunctional modifier had been successfully anchored to the polyurea backbone via covalent bonds, forming a highly hybrid chemical structure.

[0051] The disulfide bond / silane dual-modified PAE resin prepared in Example 1 had a solid content of approximately 85.4 wt% and a dynamic viscosity (25°C) of 1250 mPa·s.

[0052] Example 2: Preparation of high-proportion dual-modified PAE resin The difference from Example 1 is: (1) Material preparation: Prepare the following raw materials by weight: Polyaspartic acid ester (PAE) prepolymer: 100 parts; Isophorone diisocyanate (IPDI): 18 parts; 2,2'-Diaminodiphenyl disulfide (DAPDS): 10 parts; 3-Glycidyl etheroxypropyltrimethoxysilane (KH-560): 12 parts; Dehydrated grade butyl acetate: 50 parts.

[0053] The disulfide bond / silane dual-modified PAE resin prepared in Example 2 had a solid content of approximately 72.3 wt% and a dynamic viscosity (25°C) of 2100 mPa·s.

[0054] Comparative Example 1: Preparation of PAE Resin Without Disulfide Bonds 1) Material preparation: The difference from Example 1 is that 5 parts of DAPDS are replaced with an equimolar amount of 1,4-butanediamine. The types and amounts of the remaining raw materials (PAE prepolymer, IPDI, KH-560, butyl acetate) are exactly the same as in Example 1.

[0055] (2) Specific preparation steps: Step S1 pre-dehydration, S2 bridging reaction, step S4 side-linking and branching, and S5 finished product treatment are the same as in Example 1.

[0056] S3 chain extension reaction: Dissolve 1,4-butanediamine in half the amount of butyl acetate and slowly add it dropwise to the reactor; after the addition is complete, heat to 75°C and react for 3 hours.

[0057] The finished product specifications are: solid content of approximately 85.0 wt%; dynamic viscosity (25℃) of 1180 mPa·S.

[0058] Comparative Example 2: Preparation of PAE Resin without Silane Grafted Side Chains 1) Material preparation: The difference from Example 1 is that the reactive silane coupling agent KH-560 is not added. The types and amounts of the remaining raw materials (PAE prepolymer, IPDI, DAPDS, butyl acetate) are exactly the same as in Example 1.

[0059] (2) Specific preparation steps: Steps S1 (pre-dehydration), S2 (bridging reaction), S3 (dynamic bond insertion), and S5 (finished product processing) are the same as in Example 1.

[0060] S4: Skip the side branches and proceed directly to the next step after the S3 reaction is completed.

[0061] The finished product specifications are: solid content of approximately 84.5 wt%; dynamic viscosity (25℃) of 1050 mPa·S.

[0062] Comparative Example 3: Preparation of Physically Blended PAE Resin (1) Material preparation: The types and amounts of raw materials used are exactly the same as in Example 1, including PAE prepolymer, IPDI, DAPDS, KH-560 and butyl acetate.

[0063] (2) Specific preparation steps: Cold mixing process: All heating reaction steps are omitted. The PAE prepolymer is added to the reactor, and butyl acetate, IPDI, 3DAPDS, and KH-560 are added sequentially at room temperature (25°C). High-speed stirring (1000 rpm) is started and the mixture is mixed for 30 minutes.

[0064] Finished product processing: The product is filtered through a 200-mesh filter before being discharged.

[0065] The finished product specifications are: solid content of approximately 85.2 wt%; dynamic viscosity (25℃) of 900 mPa·S.

[0066] Example 3: Preparation of low-proportion single-end modified HDI trimer (1) Material preparation: Prepare the following raw materials by weight: HDI trimer: 100 parts; Single-hydroxyl-terminated polydimethylsiloxane: 3 parts; Dehydrated grade butyl acetate: 5 parts; Dibutyltin dilaurate (DBTDL): 0.01 parts; p-Toluenesulfonyl isocyanate (TI): 0.2 parts.

[0067] (2) Specific preparation steps: S1 Dehydration and Loading: In a four-necked reactor equipped with a stirrer, condenser, constant-pressure dropping funnel, and nitrogen gas delivery pipe, first add HDI trimer and half of butyl acetate. Start stirring and purge with high-purity nitrogen for protection, add TI dehydrating agent, and pretreat at 40°C for 30 minutes to eliminate trace amounts of moisture in the system.

[0068] S2 Catalysis and Grafting: DBTDL catalyst was added to the reactor. The single-hydroxyl-terminated silicone oil and the remaining butyl acetate were mixed evenly and then poured into a dropping funnel.

[0069] S3 Constant Temperature Reaction: Adjust the temperature inside the reactor to 70℃, and slowly add the single-ended hydroxyl silicone oil mixture. Control the dropping rate so that the temperature fluctuation of the system does not exceed 2℃. The dropping is completed in about 1 hour.

[0070] S4 Incubation and Endpoint Control: Heat to 85℃ and maintain the reaction temperature for 4 hours. During this period, take samples periodically to titrate and analyze the -NCO content in the system. Stop the reaction when the -NCO mass fraction drops to the theoretical value and tends to stabilize.

[0071] S5 Finished Product Processing: After the reaction is completed, the material is cooled to below 40°C and filtered through a 200-mesh filter to obtain the finished product.

[0072] The finished product specifications are: solid content of approximately 95.2 wt%; isocyanate group (-NCO) content of 20.6%; and dynamic viscosity (25℃) of 2620 mPa·s.

[0073] like Figure 3 The image shows the FT-IR spectrum of the finished product from Example 3, at 2270 cm⁻¹. -1 The presence of a strong -NCO characteristic absorption peak at 3300-3500 cm⁻¹ indicates that the modified component B still retains a large number of isocyanate active sites for crosslinking; -1 There was no obvious broad -OH peak in the region, and it was at 1720 cm⁻¹ -1 The presence of a carbonyl absorption peak near the urethane bond confirms that the single-hydroxyl-terminated silicone oil is completely anchored to the HDI trimer framework via chemical bonds; furthermore, the 1000-1100 cm⁻¹... -1 The strong absorption peak at that point corresponds to the Si-O-Si structure, providing physical evidence of the introduction of siloxane segments.

[0074] Example 4: Preparation of high-proportion single-end modified HDI trimer The difference from Example 1 is as follows: (1) Material preparation: Prepare the following raw materials by weight: HDI trimer: 100 parts; Single-hydroxyl-terminated polydimethylsiloxane: 15 parts; Dehydrated grade butyl acetate: 20 parts; Dibutyltin dilaurate (DBTDL): 0.08 parts; p-Toluenesulfonyl isocyanate (TI): 0.8 parts.

[0075] The finished product specifications are: solid content of approximately 84.5 wt%; isocyanate group (-NCO) content of 17.6%; and dynamic viscosity (25℃) of 2980 mPa·S.

[0076] Comparative Example 4: Preparation of HDI trimer modified with hydroxyl-terminated silicone oil (1) Material preparation: The difference from Example 3 is that an equal mass of double-hydroxyl-terminated polydimethylsiloxane (Mn approximately 2000) is used instead of single-hydroxyl-terminated silicone oil. The types and amounts of the remaining raw materials (HDI trimer, butyl acetate, DBTDL, TI) are exactly the same as in Example 3.

[0077] (2) Specific preparation steps: Step S1 dehydration and loading are the same as in Example 3.

[0078] S2 Catalysis and Grafting: DBTDL catalyst was added to the reactor. The hydroxyl-terminated silicone oil and the remaining butyl acetate were mixed evenly and then poured into a dropping funnel.

[0079] S3 isothermal reaction: Adjust the temperature inside the reactor to 70℃, and begin slowly adding the mixture of hydroxyl-terminated silicone oil. When about 2 / 3 of the volume has been added, the viscosity of the system increases rapidly, and a significant chain extension coupling reaction occurs.

[0080] S4 / S5 stage: The reaction is barely maintained until the end, and the material is in a high-viscosity gel-like state.

[0081] Comparative Example 5: Formulation of physically blended silicone oil / HDI trimer components (1) Material preparation: The types and amounts of raw materials are exactly the same as in Example 3.

[0082] (2) Specific preparation steps: Cold mixing process: All heating reaction steps are omitted. The HDI trimer is added to the reactor, and butyl acetate, TI, and single-hydroxyl-terminated silicone oil are added sequentially at room temperature (25°C). High-speed stirring is started and mixed for 30 minutes.

[0083] Finished product processing: The product is filtered through a 200-mesh filter before being discharged.

[0084] (3) Physical indicators: Appearance: Initially transparent, after standing for 48 hours, obvious oily seepage (silicone oil floating) appears on the surface.

[0085] Dynamic viscosity (25℃): 2480 mPa·s.

[0086] -NCO content: The measured value was 20.1%, which is basically consistent with the raw material.

[0087] Example 5: Preparation of Coating (1) Material preparation: Weigh each component according to Table 1.

[0088] (2) Specific preparation steps: Preparation of S1, component A: Premixing stage: Add PAE resin to the dispersion vessel, and while stirring at 800 rpm, add reactive silane coupling agent, nonionic defoamer, leveling agent and light stabilizer (if any) in sequence, and stir for 20 minutes until the components are mixed evenly; Pigment and filler dispersion stage (if applicable): Add pigments and fillers to the reactor, gradually increase the speed to 2000 rpm, and disperse at high speed for 45 minutes; Grinding stage: The dispersed slurry is fed into a sand mill for grinding until the fineness is ≤40μm; Adjustment and discharge: Add catalyst and remaining solvent, reduce speed to 500 rpm and continue stirring for 10 minutes. Filter through a 200-mesh filter to obtain component A.

[0089] Preparation of S2, component B: Environmental control: Prepare a dry, sealed reaction vessel and purge it with high-purity nitrogen to ensure that the ambient humidity (RH) is ≤40%; Mixing and dilution: Add HDI trimer, followed by slow addition of dehydrating diluent (if any); Homogenization treatment: Stir in a closed system at 500 rpm for 30 minutes to fully integrate the dehydrating agent and the modified curing agent and eliminate any trace moisture, thus obtaining component B.

[0090] S3 coating preparation (pre-application mixing ratio): Proportioning and Weighing: Mix component A and component B according to the proportions in Table 1. Mixing and curing: Slowly pour component B into component A, and stir manually or mechanically for 3-5 minutes until the system is completely homogeneous; Curing and application: After mixing evenly, let stand for 10 minutes to cure and eliminate air bubbles generated during stirring, and then apply coating to the treated substrate surface.

[0091] Table 1

[0092] Table 1 (continued)

[0093] The coatings prepared in Example 5 were subjected to performance tests, including (1) self-healing efficiency (electrochemical impedance spectroscopy, EIS). 1. Sample preparation and pretreatment Film preparation: The coating is applied to Q235 carbon steel sheets and, after complete curing, the dry film thickness is controlled to be 60±5μm.

[0094] Artificial damage: Using a micron-level scratch tester, a straight scratch 1 cm long and deep to the substrate is made on the coating surface to ensure that the substrate is exposed.

[0095] 2. Test conditions and apparatus Electrochemical workstation: Employs a standard three-electrode system. A coated steel plate serves as the working electrode (WE) (effective exposure area 1 cm²). 2 The saturated calomel electrode (SCE) is used as the reference electrode, and the platinum sheet is used as the auxiliary electrode.

[0096] Electrolyte solution: 3.5 wt% NaCl solution.

[0097] Test parameters: Disturbance signal amplitude is 10mV, frequency scan range is 10. 5 Hz to 10 -2 HZ.

[0098] 3. Testing Process Initial state (Z0): Measure the impedance modulus of the undamaged, intact coating.

[0099] Damaged state (Z) damaged ): Immediately after scratching, immerse the substrate in an electrolyte solution for EIS testing. At this time, the impedance will drop significantly due to substrate exposure.

[0100] Repair state (Z) repaired ): Place the scratched sample in a designated repair environment (60℃ constant temperature oven) for 24 hours, and then immerse it in the electrolyte solution again to measure the impedance.

[0101] 4. Data Processing and Calculation Formulas The charge transfer resistance R at the scratch was extracted by equivalent circuit fitting. ct And calculate the self-healing efficiency using the following formula: η=[(R ct(repaired) -Rct(damaged) ) / (R ct(initial) -R ct(damaged) )]*100% Where R ct(repaired) To repair the charge transfer resistor after the cycle ends.

[0102] R ct(damaged) The charge transfer resistance is measured immediately after the scratch is made.

[0103] R ct(repaired) This represents the charge transfer resistance of the original, intact coating.

[0104] (2) Static water contact angle, measured according to GB / T 30693-2014, the contact angle between plastic film and water.

[0105] (3) Salt spray test (h), ISO 9227:2017.

[0106] (4) Adhesion (pull-off method): The adhesion test of paint and varnish was conducted using the pull-off method according to GB / T 5210-2006. The results are shown in Table 2 below.

[0107] Table 2

[0108] According to the data in Table 2: 1. Causal analysis of self-repair efficiency (η) and dynamic covalent bonds The difference in self-healing efficiency mainly depends on whether the polyurea backbone contains dynamic reversible sites. Experimental data show that groups 1, 2, 7, 11, and 12 all have relatively high self-healing efficiencies, with group 12 reaching 98.2%. This is because component A resin introduces aromatic disulfide bonds ($-SS-$) through DAPDS during synthesis. At the damaged interface, these dynamic covalent bonds achieve cross-interfacial exchange of molecular chains through breaking and recombination, thereby rebuilding the physical shielding layer. In group 3, after replacing DAPDS with 1,4-butanediamine, the resulting urea bonds are irreversible covalent bonds, lacking dynamic exchange capacity, leading to a decrease in self-healing efficiency to 1.2%. Although group 5 physically does not contain DAPDS, its repair efficiency is also unsatisfactory because it does not participate in chemical cross-linking to form a continuous dynamic network, proving that the chemical bonding of disulfide bonds to the backbone is a physical prerequisite for achieving self-healing function.

[0109] 2. Mechanism analysis of static water contact angle and siloxane segment migration The differences in hydrophobic properties of the coating surface stem from the distribution of the organosilicon components. Group 12, with a contact angle of 118°, is significantly higher than other groups. Mechanistic analysis indicates that after modification with single-ended hydroxyl silicone oil, during curing, low-surface-energy polydimethylsiloxane segments are thermodynamically driven to accumulate at the air / coating interface (i.e., hydrophobic transition). Group 9 (unmodified curing agent) has a contact angle of only 74°, confirming the contribution of silicone oil grafting to reduce surface energy in component B. Furthermore, data from group 4 (no silane grafting) reflects a hydrophobic synergy between the siloxane structure provided by KH-560 and component B. Groups 11 and 12, due to the introduction of pigments and fillers, microscopically alter the surface roughness of the coating film. Combined with the low surface energy characteristics of siloxanes, this further enhances the static water contact angle, making them superior to group 1, which uses a pure resin system.

[0110] 3. Synergistic analysis of neutral salt spray resistance and overall system density Salt spray resistance is influenced by the shielding effect, adhesion, and self-healing mechanism. Groups 11 and 12 exhibited longer abnormality-free times in the ISO 9227 test. This is because the chemical dehydration effect of TI (p-toluenesulfonyl isocyanate) eliminated moisture interference, ensuring that the isocyanate groups (-NCO) reacted with the secondary amines to form a dense polyurea network, reducing microporous defects; the physical barrier formed by ultrafine barium sulfate particles within the coating extended the penetration path of the corrosive medium. Group 4, lacking a silane coupling agent, suffered from insufficient interfacial bonding, allowing the corrosive medium to easily spread laterally from the scratches, resulting in peeling after 1000 hours. Group 8 (physically blended silicone oil) failed after 750 hours due to the poor compatibility of the free silicone oil with the system, which disrupted the continuity of the coating film. The experimental results demonstrate that the combination of the repair network formed by chemical grafting and the deep dehydration process is the main reason for maintaining long-term shielding performance.

[0111] 4. Logical Analysis of Adhesion (Pull-off Method) and Interfacial Chemical Anchoring The adhesion test results are mainly affected by the density of interfacial covalent bonds. Group 12 achieved an adhesion of 9.5 MPa. The epoxy silane functional groups at the ends of component A resin (introduced by KH-560) can form Fe-O-Si covalent bonds with the hydroxyl groups on the surface of the metal substrate through a condensation reaction, anchoring the organic coating to the inorganic substrate. Group 4, lacking this component, showed a decrease in adhesion to 3.2 MPa, exhibiting interfacial damage characteristics, indicating that physical adsorption cannot support heavy-duty anti-corrosion requirements. Comparing Group 11 with Group 1, it can be observed that the active sites on the surface of pigments and fillers can also react with the silane groups in the resin, enhancing the cohesive force within the paint film. This dual reinforcement effect of the interface and the interior explains the experimental phenomenon that the pigment-filler-containing system outperforms the pure resin system in adhesion.

[0112] Additional comparative experiments To ensure the stability of this invention in high humidity environments, a construction performance test in such an environment was specifically added, specifically: 1. Experimental conditions Environmental simulation: The Q235 steel plate to be coated is placed in a constant temperature and humidity chamber (temperature 25℃, relative humidity 90±2%) for 24 hours to pre-treat and form a trace amount of physically adsorbed water film on the surface of the substrate.

[0113] Construction process: The coating is mixed and applied in the above-mentioned high humidity environment, and cured for 45 hours under the same humidity conditions.

[0114] Test indicators: The adhesion test was conducted using the pull-out method according to GB / T5210-2006, and the presence of microbubbles or pinholes in the paint film was observed.

[0115] The results are shown in Table 3 below.

[0116] Table 3 shows that the adhesion retention rate under high humidity conditions reflects the coating's tolerance and conversion ability to interfacial moisture. Experimental results show that under harsh conditions of relative humidity ≥90%, the adhesion of group 11 only fluctuated slightly from 9.2 MPa to 8.8 MPa, and the paint film remained dense. The principle is that the KH-560 alkoxysilane structure grafted in component A has high interfacial moisture sensitivity. Adsorbed water on the substrate surface induces in-situ hydrolysis of silane groups, and the generated silanol then forms a strong Fe-O-Si covalent bond with the hydroxyl groups on the metal surface. This mechanism transforms harmful interfacial water into a coupling agent that promotes chemical anchoring, thereby avoiding hydrogen bond failure caused by moisture accumulation at the interface.

[0117] In contrast, Group 4 (without silane modification) lacked a moisture conversion mechanism, and the interfacial moisture hindered the physical polar adsorption between the polyurea network and the substrate, resulting in a sharp drop in adhesion. Simultaneously, observation of Group 9 data revealed that the absence of the chemical dehydration effect of TI (p-toluenesulfonyl isocyanate) led to micropores in the paint film and a significant decrease in adhesion. This invention, through the synergistic design of "interfacial silanization conversion" and "bulk chemical dehydration," eliminates the competitive reaction interference of moisture on isocyanate groups under high humidity construction conditions, ensuring the integrity of the crosslinked network.

[0118] The above detailed description is a specific description of one of the feasible embodiments of the present invention. This embodiment is not intended to limit the patent scope of the present invention. All equivalent implementations or modifications that do not depart from the present invention should be included within the scope of the technical solution of the present invention.

Claims

1. A polyurea-modified polysiloxane anticorrosive coating, characterized in that, The following components are included in parts by mass: Component A: Disulfide bond / silane dual-modified PAE resin 100 Reactive silane coupling agent 1.5-3.0 Catalyst 0.1-0.5 Component B: Single-hydroxyl-terminated silicone oil modified HDI trimer 45-55 The disulfide bond / silane dual-modified PAE resin is a hybrid resin formed by the addition reaction of polyaspartic acid ester, diisocyanate and diamine containing disulfide bonds to form a main chain containing urea bonds and disulfide bonds, and the addition of residual isocyanate groups on the side chain with aminoalkoxysilane to construct siloxane branches. The single-hydroxyl-terminated silicone oil modified HDI trimer is a prepolymer containing active isocyanate groups formed by the addition reaction of HDI trimer and single-hydroxyl-terminated polydimethylsiloxane, in which the siloxane segments are chemically anchored to the isocyanate backbone through urethane bonds.

2. The polyurea-modified polysiloxane anticorrosive coating according to claim 1, characterized in that, Component B also contains 5-15 parts of a dehydrating diluent.

3. The polyurea-modified polysiloxane anticorrosive coating according to claim 1, characterized in that, Component A also contains 10-25 parts of filler and 5-15 parts of pigment; the filler is a component that increases the thickness and hardness of the paint film; the pigment is a component that provides hiding power and color matching.

4. The polyurea-modified polysiloxane anticorrosive coating according to claim 1, characterized in that, Component A also contains 0.2-0.5 parts of nonionic defoamer; 0.3-0.8 parts of leveling agent; and 0.5-1.2 parts of light stabilizer.

5. The polyurea-modified polysiloxane anticorrosive coating according to claim 1, characterized in that, The preparation steps of the disulfide bond / silane dual-modified PAE resin include: S1, Place the polyaspartic acid ester resin into the reaction vessel and perform dehydration pretreatment; S2, Inert gas is introduced into the reaction vessel, and aliphatic diisocyanate is added to carry out a bridging reaction; S3, a diamine containing a disulfide bond is added to the system to carry out a dynamic bond intercalation reaction; S4, add aminoalkoxysilane to the system, keep the reaction at a constant temperature; add organic solvent to adjust the solid content, and filter out the material.

6. The polyurea-modified polysiloxane anticorrosive coating according to claim 5, characterized in that, The mass ratio of the polyaspartic ester resin, aliphatic diisocyanate, diamine containing disulfide bonds, aminoalkoxysilane, and organic solvent is 100:8-18:3-10:2-12:20-50.

7. The polyurea-modified polysiloxane anticorrosive coating according to claim 1, characterized in that, The preparation steps of the single-hydroxyl-terminated silicone oil modified HDI trimer include: S1, add HDI trimer and organic solvent to the reaction vessel, and introduce inert gas; S2, add the esterification catalyst to the reaction vessel and stir until homogeneous; S3, add single-hydroxyl-terminated silicone oil to the reaction vessel for grafting reaction, and then heat to ripen; S4, after maturation, is cooled and discharged.

8. The polyurea-modified polysiloxane anticorrosive coating according to claim 7, characterized in that, The mass ratio of the HDI trimer, single-hydroxyl-terminated silicone oil, urethane catalyst, and organic solvent is 100:3-15:0.01-0.08:5-20; the number average molecular weight of the single-hydroxyl-terminated silicone oil is between 1000 and 5000.

9. The polyurea-modified polysiloxane anticorrosive coating according to claim 1, characterized in that, The mixing ratio of component A to component B, expressed as an NCO / NH molar ratio, is 1.05-1.10:

1.

10. The method for preparing the polyurea-modified polysiloxane anticorrosive coating according to any one of claims 1-9, characterized in that, Including the following steps: (1) Preparation of component A: Take the disulfide bond / silane dual-modified PAE resin, add reactive silane coupling agent, catalyst and other components in sequence, disperse or grind at high speed to fineness ≤40μm to obtain uniform component A; (2) Preparation of component B: Take the single-hydroxyl-terminated silicone oil modified HDI trimer, add a dehydrating diluent as needed, and mix evenly to obtain component B; (3) Coating molding: Before use, the A component and the B component are mixed and stirred evenly to obtain the polyurea modified polysiloxane anti-corrosion coating.

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