Preparation of self-repairing polyurethane resin and application of self-repairing polyurethane resin in anti-corrosion damping coating

Abstract

The invention relates to damping paint, in particular to preparation of self-repairing polyurethane resin and application of the self-repairing polyurethane resin to anticorrosive damping paint. According to the invention, the modified isocyanate resin is obtained by modifying the existing isocyanate, and then the self-repairing polyurethane anti-corrosion damping coating with strong self-repairing capability is obtained by taking the modified isocyanate resin as a curing agent of the coating. According to the coating provided by the invention, a multi-stage dynamic cross-linked network is constructed through the synergistic effect of triple dynamic bonds, i.e., disulfide bonds, hydrogen bonds and coordinate bonds; the three components cooperate to significantly improve the self-repairing efficiency of the material, the mechanical property recovery rate after repairing exceeds that of a traditional single / double bond system, and the problems of damping performance attenuation and corrosion medium permeation caused by microcracks generated after long-term vibration or mechanical damage of a traditional damping coating are solved.

Description

Technical Field

[0001] This invention relates to a damping coating, and more specifically, to the preparation of a self-healing polyurethane resin and its application as an anti-corrosion damping coating. Background Technology

[0002] Damping coatings are functional materials that dissipate mechanical vibration energy through the viscoelasticity of polymer materials. They are widely used in rail transportation, aerospace, and marine equipment to reduce vibration noise and extend equipment life. Traditional damping coatings are prone to microcracks after long-term vibration or mechanical damage, leading to a decline in damping performance and the penetration of corrosive media. Although progress has been made in self-healing coating technology, its application in damping systems remains limited.

[0003] Current self-healing technologies mainly rely on the release of microcapsule corrosion inhibitors or dynamic chemical bond recombination, but these have limitations. Patent CN105925129A uses mesoporous silica nanocapsules to encapsulate corrosion inhibitors, achieving localized repair, but the microcapsules have poor compatibility with the substrate, easily leading to a decrease in coating density. Patent CN118307482A achieves self-healing through a hydrogen bond network, but the low bond energy of individual hydrogen bonds makes them prone to failure under high temperature or high humidity environments. Meanwhile, high-solids-content waterborne coatings are becoming an environmentally friendly trend due to their low VOC characteristics, but their formulation design faces challenges. Patent CN105860719A uses a compound of hollow glass microspheres and mica powder to broaden the damping temperature range, but the high filler content leads to deterioration of rheological properties. Furthermore, metal substrates are prone to localized corrosion due to microcracks under vibration environments, and existing anti-corrosion damping coatings mostly focus on a single function. Patent CN118307482A utilizes a hydrogen bond self-healing mechanism to delay corrosion diffusion, but its solid content is only 40-50%, which is difficult to meet the requirements of high-load scenarios. Patent CN105860719A uses fluorosilicone polymers to achieve low surface energy corrosion protection, but its hydrophobicity conflicts with the viscoelastic energy dissipation mechanism of damping materials.

[0004] In summary, current research and development of damping coatings suffers from insufficient self-healing capabilities and low corrosion resistance, necessitating breakthroughs through material design and process innovation. Summary of the Invention

[0005] To address the technical problem of insufficient self-healing ability in existing damping coatings, this invention provides a method for preparing a self-healing polyurethane resin and its application as an anti-corrosion damping coating.

[0006] This invention modifies existing isocyanates to obtain a modified isocyanate resin, and then uses the modified isocyanate resin as a curing agent for coatings to obtain a self-healing polyurethane anti-corrosion damping coating with strong self-healing ability.

[0007] One of the objectives of this invention is to provide a modified isocyanate resin.

[0008] The chemical formula of the modified isocyanate resin is: OCN-R3-NHCO-O-R1-NHCO-R2-CONH-R1-O-CONH-R3-NCO; in, O-R1-NH is derived from polyhydrobonded pyrimidines; CO-R2-CO is derived from a disulfide chain extender containing two carboxyl groups; CONH-R3-NCO is derived from diisocyanate.

[0009] The polyhydrogen-bonded pyrimidine is selected from , , , At least one of them.

[0010] The disulfide chain extender is selected from... , , , At least one of them.

[0011] The diisocyanate is selected from , , , At least one of them.

[0012] As a preferred embodiment, the polyhydrogen-bonded pyrimidine is 2-amino-4-hydroxy-6-methylpyrimidine or 4-amino-6-hydroxy-2-mercaptopyrimidine, the disulfide chain extender is dithioglycolic acid or 3,3'-dithiodipropionic acid, and the diisocyanate is hexamethylene diisocyanate or isophorone diisocyanate.

[0013] As a specific embodiment, the modified isocyanate resin has the following structural formula: .

[0014] The modified isocyanate resin can be obtained by reacting polyhydrogen-bonded pyrimidines, disulfide chain extenders, and diisocyanates.

[0015] A second objective of this invention is to provide a method for preparing the modified isocyanate resin described in one of the objectives of this invention.

[0016] The method for preparing the modified isocyanate resin includes: reacting the disulfide chain extender with the polyhydrogen-bonded pyrimidine via an amidation reaction to generate the modified chain extender; and reacting the modified chain extender with diisocyanate via a carbamate reaction to generate the modified isocyanate resin.

[0017] The carbamate reaction refers to the reaction between the hydroxyl groups on the modified chain extender and the isocyanate groups on the isocyanate.

[0018] Taking 2-amino-4-hydroxy-6-methylpyrimidine as the polyhydrogen-bonded pyrimidine, disulfide chain extender as dithioglycolic acid, and diisocyanate as hexamethylene diisocyanate as an example, the reaction equation for the preparation method is as follows:

[0019] Formula 1 is a modified chain extender, and Formula 2 is a modified isocyanate resin.

[0020] The preparation method may include the following steps: 1) Dissolve disulfide chain extender and polyhydrogen-bonded pyrimidine in a solvent, add catalyst A, and stir the reaction under an inert atmosphere; 2) After the reaction is complete, filter the solution, add dilute hydrochloric acid to the filtrate, then add molecular sieves, stir, filter again, and collect the filtrate. 3) Add diisocyanate and catalyst B to the filtrate and stir the reaction under an inert atmosphere; 4) After the reaction is complete, remove the solvent to obtain the modified isocyanate resin.

[0021] In step 1), the disulfide chain extender reacts with the polyhydrogen-bonded pyrimidine in a solvent under the action of a catalyst at room temperature and pressure. Each molecule of disulfide chain extender reacts with one molecule of polyhydrogen-bonded pyrimidine at both ends to generate a modified chain extender.

[0022] In step 1), the solvent is selected from at least one of dimethyl sulfoxide, dichloromethane, xylene, and butyl acetate.

[0023] In step 1), catalyst A is selected from the DCC / DMAP catalyst system composed of dicyclohexylcarbodiimide (DCC) and 4-N,N-dimethylpyridine (DMAP).

[0024] In step 1), one molecule of disulfide chain extender reacts with two molecules of multi-hydrogen bonded pyrimidine. Therefore, the molar ratio of the disulfide chain extender to the multi-hydrogen bonded pyrimidine can be 1:2.

[0025] In step 1), the molar ratio of the disulfide chain extender to DCC in catalyst A can be 1:1.5~2.5, for example, 1:1.8, 1:2, or 1:2.3. In step 1), the molar ratio of the disulfide chain extender to DMAP in catalyst A is 1:0.12~0.18, for example 1:0.15.

[0026] In step 1), the inert atmosphere is a nitrogen atmosphere.

[0027] In step 1), the reaction ends when the amount of precipitate in the system no longer increases. The carboxyl group in the disulfide chain extender reacts with the amino group in the pyrimidine compound (R-NH2 + R'-COOH = R'-CONH-R + H2O) to form an amide bond and water. To promote the reaction, a DCC dehydrating agent is added, which combines with the water generated in the amidation reaction to form an insoluble DCU (dicyclohexylurea) byproduct (precipitate). The reaction ends when the amount of DCU (dicyclohexylurea) byproduct no longer increases.

[0028] The reaction time for step 1) can be 2 to 4 hours.

[0029] In step 2), after the reaction is complete, the reaction system contains the product-modifying chain extender, solvent, byproduct DCU, and unreacted DCC and DMAP. Filtering removes insoluble matter (DCC, byproduct DCU), and the filtrate contains the product-modifying chain extender, solvent, and DMAP. Hydrochloric acid is added to the filtrate; the hydrochloric acid reacts with DMAP to form a water-soluble salt. Molecular sieves are added; while removing water, the water-soluble salt precipitates. Filtering removes the molecular sieves and the precipitated water-soluble salt at the same time. At this point, the remaining filtrate contains the product-modifying chain extender and solvent. The filtrate collected in step 2) is the modified chain extender solution; that is, after step 2), a modified chain extender solution is obtained; the solvent for the modified chain extender solution is the solvent added in step 1).

[0030] In step 2), the concentration of dilute hydrochloric acid can be any concentration; specifically, it can be pH=3.

[0031] In step 2), the molecular sieve serves to adsorb water, and any existing molecular sieve can be selected. Specifically, the molecular sieve is selected from either a 4Å or 5Å molecular sieve.

[0032] In step 3), the diisocyanate reacts with the modified chain extender in the filtrate under the action of catalyst B at room temperature and pressure. Each molecule of modified chain extender reacts with one molecule of diisocyanate at both ends to generate modified isocyanate resin.

[0033] In step 3), the catalyst B is selected from dibutyltin dilaurate.

[0034] In step 3), the inert atmosphere is a nitrogen atmosphere.

[0035] In step 3), one modified chain extender molecule reacts with two diisocyanate molecules, and one modified chain extender molecule is generated from one disulfide chain extender molecule. Therefore, the molar ratio of the disulfide chain extender to the diisocyanate is 1:2, but in practice it can be 1:2 to 2.2.

[0036] In step 3), the mass ratio of the diisocyanate to catalyst B can be 1:0.001~0.01, for example 1:0.002, 1:0.005, or 1:0.008.

[0037] The reaction time for step 3) can be 5 to 7 hours.

[0038] In step 4), after the reaction is complete, the reaction system contains modified isocyanate resin, solvent, a small amount of catalyst B, and a small amount of unreacted diisocyanate. The presence of the small amount of catalyst B and the small amount of unreacted diisocyanate does not affect the performance of the modified isocyanate resin as a coating component. Therefore, the modified isocyanate resin can be obtained simply by removing the solvent from the reaction system.

[0039] In step 4), the methods for removing the solvent include: vacuum freeze drying or rotary evaporation.

[0040] One method for preparing the modified cyanate ester resin includes: 1) Dissolve the disulfide chain extender and the polyhydrogen-bonded pyrimidine in dimethyl sulfoxide (DMSO), stir until homogeneous, add catalyst A, and stir the reaction for 2-4 hours under a nitrogen atmosphere. 2) After the reaction is complete, filter the solution, add dilute hydrochloric acid with pH=3 to the solution, add 4Å molecular sieve, stir for 0.5~1h, filter, collect the filtrate, and obtain the DMSO solution of modified chain extender. 3) Add diisocyanate resin and catalyst B to the DMSO solution of modified chain extender, and stir the reaction for 5-7 hours under a nitrogen protective atmosphere to obtain the DMSO solution of modified cyanate resin. 4) Use vacuum freeze-drying or rotary evaporation to remove DMSO from the DMSO solution of the modified cyanate ester resin to obtain the modified cyanate ester resin.

[0041] The third objective of this invention is to provide a self-healing polyurethane anti-corrosion damping coating.

[0042] The self-healing polyurethane anti-corrosion damping coating comprises component A and component B. Component A contains polytetrahydrofuran resin, pigments, fillers, additives, and diluent A; Component B contains isocyanate resin, catalyst C, and diluent B; The molar ratio of OH in component A to NCO in component B is 1:1.02~1.06, for example 1:1.03, 1:1.04, 1:1.05; The isocyanate resin is selected from the modified isocyanate resin described in one of the invention objectives or the modified isocyanate resin prepared by the preparation method described in another of the invention objectives.

[0043] In component A, polytetrahydrofuran resin is the main component. The amounts of other components are determined based on the amount of polytetrahydrofuran resin. The amounts of pigments, fillers, additives, and diluent A can all be the conventional amounts. As a preferred embodiment, component A, by weight, comprises: 100 parts of polytetrahydrofuran resin; Pigments and fillers: 20-100 parts, for example, 30, 40, 50, 60, 70, 80, or 90 parts; Additives: 1 to 10 parts, for example, 2, 3, 4, 5, 6, 7, 8, or 9 parts; Diluent A is available in quantities of 10-70, such as 20, 30, 40, 50, or 60 parts.

[0044] In component B, isocyanate resin is the main component. The isocyanate resin undergoes a curing reaction with the polytetrahydrofuran resin in component A. The amounts of other components are determined based on the amount of isocyanate resin. The amounts of catalyst C and diluent B can be the conventional amounts. As a preferred embodiment, component B, by weight, comprises: 100 parts of isocyanate resin; Catalyst C: 0.5-2 parts, for example, 0.8, 1, 1.2, 1.5, or 1.8 parts; Diluent B is used in 10 to 50 parts, for example, 20, 30, or 40 parts by weight.

[0045] In component A, the number-average molecular weight of the polytetrahydrofuran resin is less than or equal to 2000, for example, 250, 600, or 1000. When the number-average molecular weight of the polytetrahydrofuran resin is greater than 2000, the prepared coating has excessive fluidity, which is not conducive to product application, has low tensile strength, low dynamic loss, and insufficient damping performance; at the same time, products with a molecular weight of 2000 are more expensive. When the number-average molecular weight of the polytetrahydrofuran resin is less than or equal to 200, the prepared coating has extremely high viscosity, which brings additional difficulties to use and processing, and has the risk of explosive polymerization causing a decline in coating performance. Additionally, the coating has high strength, poor toughness, and low self-healing properties.

[0046] In component A, the additive can be any one or more existing additives that can be added to self-healing coatings, such as at least one selected from wetting and dispersing agents, defoamers and leveling agents.

[0047] The wetting and dispersing agent can be any one or more existing wetting and dispersing agents, specifically selected from at least one of BYK-104S, BYK-190, BYK-191, and BYK-2205.

[0048] The defoamer can be any one or more existing defoamers, specifically selected from at least one of BYK-024, BYK-054, BYK-088, and BYK-LP D24043.

[0049] The leveling agent can be any one or more existing leveling agents, specifically selected from at least one of BYK-331, BYK-354, BYK-358N, and BYK-399.

[0050] In component A, the pigments and fillers can be any one or more existing pigments and fillers, such as at least one selected from talc, heavy calcium carbonate, mica powder, iron oxide red, aluminum tripolyphosphate, basalt, zinc phosphate, precipitated barium sulfate, and bentonite. As a preferred embodiment, the pigments and fillers are selected from phosphate-based anti-corrosion pigments and fillers, thereby further enhancing the anti-corrosion performance of the coating.

[0051] In component A, the diluent A is selected from at least one of benzene-based diluents, ketone-based diluents, and ester-based diluents.

[0052] In component B, the diluent B is selected from at least one of benzene-based diluents, ketone-based diluents, and ester-based diluents. Diluent B may be the same as or different from diluent A.

[0053] In component B, catalyst C can be any one or more existing catalysts used for catalyzing the curing reaction of isocyanate and polytetrahydrofuran resin. Preferably, catalyst C is selected from at least one of dibutyltin dilaurate and stannous octoate.

[0054] The fourth objective of this invention is to provide a method for preparing the self-healing polyurethane anti-corrosion damping coating described in the third objective of this invention.

[0055] The preparation method of the self-healing polyurethane anti-corrosion damping coating includes: 1) Add additives and diluent A to polytetrahydrofuran resin, disperse evenly, add filler, disperse evenly, and obtain component A; 2) Mix the isocyanate resin, catalyst C, and diluent evenly to obtain component B; 3) After mixing component A and component B evenly according to the ratio, the self-healing polyurethane anti-corrosion damping coating is obtained.

[0056] Compared with the prior art, the beneficial effects of the present invention are as follows: 1) A multi-level dynamic cross-linked network was constructed through the synergistic effect of three dynamic bonds: disulfide bonds, hydrogen bonds, and coordination bonds. Disulfide bonds provide reversible covalent bond repair capability, hydrogen bonds enable rapid self-healing at room temperature, and coordination bonds enhance network stability and impart external force response characteristics. The synergistic effect of these three bonds significantly improves the self-healing efficiency of the material, and the recovery rate of mechanical properties after repair exceeds that of traditional single / double bond systems. This solves the problem of damping performance degradation and corrosive medium penetration caused by microcracks in traditional damping coatings after long-term vibration or mechanical damage.

[0057] 2) This invention prepares an anti-corrosion damping coating through innovative formula design. By introducing phosphate-based anti-corrosion pigments and fillers, the anti-corrosion performance of the coating is enhanced, avoiding safety risks and damping performance failure caused by corrosion damage. It is suitable for vibration reduction of rail transit equipment and corrosion protection of ship hulls.

[0058] 3) By modifying isocyanate, the self-healing, anti-corrosion (salt spray resistance) and damping properties of the coating formed by it are improved. Attached Figure Description

[0059] Figure 1 This is a synthesis route diagram of the self-healing polyurethane in Embodiment 1 of the present invention. Detailed Implementation

[0060] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0061] All reagents used in the following examples and comparative examples are commercially available products. The diluent used was a mixed diluent prepared from xylene and butyl acetate in a ratio of 6:4 (by weight).

[0062] In the following examples and comparative examples, all parts are by weight.

[0063] Example 1 1) Weigh 9.11 g of dithioglycolic acid and 12.51 g of 2-amino-4-hydroxy-6-methylpyrimidine, and dissolve them in 200 g of dimethyl sulfoxide (DMSO); then add 20.6 g of dicyclohexylcarbodiimide (DCC) and 0.61 g of 4-N,N-dimethylpyridine (DMAP), and stir until dissolved; under nitrogen protection, stir the reaction for 3 hours.

[0064] 2) After the reaction is complete, remove the insoluble matter (DCC, byproducts) in the solution by suction filtration; add 5 ml of dilute hydrochloric acid with pH=3 and stir for 30 minutes; then add 20 g of 4 Å molecular sieve, stir for 30 minutes and filter to obtain a DMSO solution of modified chain extender.

[0065] 3) Add 33.64 g of hexamethylene diisocyanate and 0.2 g of dibutyltin dilaurate to the DMSO solution of the modified chain extender, and stir the reaction for 5 h under nitrogen protection.

[0066] 4) After the reaction is complete, the DMSO in the solution is removed by rotary evaporation to obtain the modified isocyanate resin.

[0067] 5) Weigh 100 parts of modified isocyanate resin, add 1 part of dibutyltin dilaurate and 15 parts of diluent, stir evenly to obtain component B.

[0068] 6) Weigh 50 parts of polytetrahydrofuran-1000 and place it in a slurry tank. Dry it in a vacuum oven at 100°C for 2 hours. While stirring at high speed (300 rpm), add 0.2 parts of defoamer BYK-024, 0.5 parts of wetting and dispersing agent BYK-2205, 0.3 parts of leveling agent BYK-331, 10 parts of talc, 15 parts of zinc phosphate, and 20 parts of diluent to the slurry tank in sequence. Stir evenly, grind it to a fineness of 80 μm using a three-roll mill, filter it, and obtain component A.

[0069] 7) Weigh component A and component B according to the ratio of n(OH):n(NCO)=1:1.04 (molar ratio), mix them evenly, and obtain a polyurethane coating with self-healing function.

[0070] 8) Apply the self-healing polyurethane coating to the surface of the carbon steel test sample, with a dry film thickness of 200 μm, and cure at 70°C for 24 hours to obtain a self-healing polyurethane coating.

[0071] The reaction route diagram from step 1) to step 8) is as follows: Figure 1 As shown. Figure 1 In the formula, Formula 1 is the modified chain extender, Formula 2 is the modified isocyanate resin, and Formula 3 is the main component of the polyurethane coating (the curing reaction product of the modified isocyanate resin and polytetrahydrofuran-1000).

[0072] The self-healing polyurethane coating prepared in this embodiment was subjected to infrared analysis. The results showed that the coating had a high infrared sensitivity in the range of 2260–2280 cm⁻¹. -1 Within the range, no characteristic peak representing -NCO was observed, indicating that the modified isocyanate resin in the self-healing polyurethane coating had completely reacted; at 1147 cm⁻¹ -1The characteristic peak appearing at 1733 cm⁻¹ is the ether bond in polytetrahydrofuran-1000; -1 The characteristic peaks at 1531 cm⁻¹ and 1531 NH₄⁻ represent the synthesis of the polyurethane backbone; at 3314 cm⁻¹... -1 The broad peak at 1476 cm⁻¹ indicates the presence of numerous hydrogen bonds in the system; -1 The peak appearing at [value] indicates the formation of Zn-N coordination bonds; throughout the process, disulfide bonds do not participate in the reaction, as shown by the peak at 518 cm⁻¹ in the test. -1 Characteristic peaks.

[0073] Example 2 1) Weigh 10.51g of 3,3'-dithiodipropionic acid and 16.12g of 4-amino-6-hydroxy-2-mercaptopyrimidine and dissolve them in 200g of DMSO; then add 20.6g of DCC and 0.61g of DMAP and stir until dissolved; under nitrogen protection, stir the reaction for 2.5 hours.

[0074] 2) After the reaction is complete, remove the insoluble matter in the solution by suction filtration; add 5 ml of dilute hydrochloric acid with pH=3 and stir for 30 minutes; then add 20 g of 4 Å molecular sieve, stir for 30 minutes and filter to obtain a DMSO solution of modified chain extender.

[0075] 3) Add 44.46 g of isophorone diisocyanate and 0.2 g of dibutyltin dilaurate to the DMSO solution of the modified chain extender, and stir the reaction for 4 h under nitrogen protection.

[0076] 4) After the reaction is complete, the DMSO in the solution is removed by rotary evaporation to obtain the modified isocyanate resin.

[0077] 5) Weigh 100 parts of modified isocyanate resin, add 1 part of dibutyltin dilaurate and 10 parts of diluent, stir evenly to obtain component B.

[0078] 6) Weigh 50 parts of polytetrahydrofuran-650 and place them in a slurry tank. Dry them in a vacuum oven at 100°C for 2 hours. While stirring at high speed (300 rpm), add 0.5 parts of defoamer BYK-088, 0.3 parts of wetting and dispersing agent BYK-104S, 0.4 parts of leveling agent BYK-358N, 15 parts of zinc phosphate, and 15 parts of diluent to the slurry tank in sequence. Stir evenly, grind to a fineness of 80 μm using a three-roll mill, filter, and obtain component A.

[0079] 7) Weigh component A and component B according to the ratio of n(OH):n(NCO)=1:1.03, mix them evenly, and obtain a polyurethane coating with self-healing function.

[0080] 8) Apply the self-healing polyurethane coating to the surface of the carbon steel test sample, with a dry film thickness of 200 μm, and cure at 70°C for 24 hours to obtain a self-healing polyurethane coating.

[0081] Example 3 1) Weigh 9.11g of dithioglycolic acid and 12.71g of 2-amino-4,6-dihydroxypyrimidine and dissolve them in 200g of DMSO; then add 20.6g of DCC and 0.61g of DMAP and stir until dissolved; under nitrogen protection, stir the reaction for 2.5 hours.

[0082] 2) After the reaction is complete, remove the insoluble matter in the solution by suction filtration; add 5 ml of dilute hydrochloric acid with pH=3 and stir for 30 minutes; then add 20 g of 4 Å molecular sieve, stir for 30 minutes and filter to obtain a DMSO solution of modified chain extender.

[0083] 3) Add 69.60 g of toluene diisocyanate and 0.3 g of dibutyltin dilaurate to the DMSO solution of the modified chain extender, and stir the reaction for 4 h under nitrogen protection.

[0084] 4) After the reaction is complete, the DMSO in the solution is removed by rotary evaporation to obtain the modified isocyanate resin.

[0085] 5) Weigh 100 parts of modified isocyanate resin, add 1.1 parts of dibutyltin dilaurate and 25 parts of diluent, stir evenly to obtain component B.

[0086] 6) Weigh 50 parts of polytetrahydrofuran-650 and place them in a slurry tank. Dry them in a vacuum oven at 100°C for 2 hours. While stirring at high speed (300 rpm), add 0.5 parts of defoamer BYK-054, 1 part of wetting and dispersing agent BYK-191, 0.5 parts of leveling agent BYK-354, 10 parts of talc, 15 parts of zinc phosphate, 25 parts of mica powder, 5 parts of 200-mesh basalt, 5 parts of heavy calcium carbonate, and 15 parts of diluent to the slurry tank in sequence. Stir evenly, grind to a fineness of 80 μm using a three-roll mill, filter, and obtain component A.

[0087] 7) Weigh out component A and component B according to the ratio of n(OH):n(NCO)=1:1.05, mix them evenly, and obtain a polyurethane coating with self-healing function.

[0088] 8) Apply the self-healing polyurethane coating to the surface of the carbon steel test sample, with a dry film thickness of 200 μm, and cure at 70°C for 24 hours to obtain a self-healing polyurethane coating.

[0089] Example 4 1) Weigh 15.32g of 2,2'-dithiodibenzoic acid and 15.82g of 4,5-diamino-2-thiouracil and dissolve them in 200g of DMSO; then add 20.6g of DCC and 0.61g of DMAP and stir until dissolved; under nitrogen protection, stir the reaction for 2.5 hours.

[0090] 2) After the reaction is complete, remove the insoluble matter in the solution by suction filtration; add 5 ml of dilute hydrochloric acid with pH=3 and stir for 30 minutes; then add 20 g of 4 Å molecular sieve, stir for 30 minutes and filter to obtain a DMSO solution of modified chain extender.

[0091] 3) Add 50.01 g of diphenylmethane diisocyanate and 0.2 g of dibutyltin dilaurate to the DMSO solution of the modified chain extender, and stir the reaction for 4 h under nitrogen protection.

[0092] 4) After the reaction is complete, the DMSO in the solution is removed by rotary evaporation to obtain the modified isocyanate resin.

[0093] 5) Weigh 100 parts of modified isocyanate resin, add 0.7 parts of dibutyltin dilaurate and 30 parts of diluent, stir evenly to obtain component B.

[0094] 6) Weigh 50 parts of polytetrahydrofuran-650 and place them in a slurry tank. Dry them in a vacuum oven at 100°C for 2 hours. While stirring at high speed (300 rpm), add 0.5 parts of defoamer BYK-LP D24043, 0.5 parts of wetting and dispersing agent BYK-2205, 1.5 parts of leveling agent BYK-399, 1 part of inorganic bentonite, 4 parts of aluminum tripolyphosphate, 5 parts of precipitated barium sulfate, 10 parts of basalt, 10 parts of heavy calcium carbonate, 15 parts of zinc phosphate, 15 parts of mica powder, and 30 parts of diluent to the slurry tank in sequence. Stir evenly, grind to a fineness of 80 μm using a three-roll mill, filter, and obtain component A.

[0095] 7) Weigh out component B and component B according to the ratio of n(OH):n(NCO)=1:1.04, mix them evenly, and obtain a polyurethane coating with self-healing function.

[0096] 8) Apply the self-healing polyurethane coating to the surface of the carbon steel test sample. The dry film thickness is 200 μm. Cure at 70°C for 24 hours to obtain a self-healing polyurethane coating.

[0097] Comparative Example 1 1) Add 1.74 g (15 mmol) of dimethylglyoxime (chain extender), 3.33 g (15 mmol) of isophorone diisocyanate, and 100 mL of dibutyltin dilaurate to a three-necked flask, and then add 5 mL of N,N-dimethylformamide as a solvent. Place the three-necked flask in an oil bath at 80 °C for 3 h, and purify the three-necked flask with nitrogen as a protective atmosphere throughout the process.

[0098] 2) Add 10g of polytetrahydrofuran-1000, which has been vacuum dried at 120℃ for 2h, and 5mL of N,N-dimethylformamide to the above prepolymer, and then continue the reaction at 80℃ for 3h.

[0099] 3) Add 2.22 g (10 mmol) of isophorone diisocyanate to a three-necked flask, and continue the reaction at 60 °C for 12 hours. Pour the resulting viscous product into a polytetrafluoroethylene mold and dry it in a vacuum oven at 80 °C for 48 hours to obtain polyurethane elastomer.

[0100] Comparative Example 2 1) 10 parts by weight of polytetrahydrofuran (PTMEG1000) with a molecular weight of 1000 (number average molecular weight) were dehydrated under vacuum at 110°C. After 2 hours, the heating was turned off and N2 was introduced for protection. After the temperature dropped to 80°C, 4.5 parts by weight of 3-isocyanate-methylene-3,5,5-trimethylcyclohexyl isocyanate (IPDI) were added. At the same time, 0.02 parts by weight of catalyst dibutyltin dilaurate (DBTDL) and 2 parts by weight of N,N'-dimethylformamide (DME) were added to adjust the viscosity of the reactants. After reacting at 85°C for 4 hours, the prepolymer was obtained.

[0101] 2) Weigh 0.9 parts by weight of 2,2'-dithiodibenzoic acid (DTSA), dissolve it completely in 4 parts by weight of DMF, and add it to the prepolymer obtained in step 1) (the weight of the prepolymer is equivalent to 14.5). Under N2 protection, react at 80°C for 6 hours to obtain the preliminary chain-extended product.

[0102] 3) Weigh 0.7 parts by weight of 2,6-diaminopyridine (DAP), dissolve it completely in 4 parts by weight of DMF, and add it to the product obtained in step (2). Under N2 protection, stir rapidly at 60°C for 10 minutes, pour it into a polytetrafluoroethylene mold to form a plate, and keep it at 60°C for 6 hours under vacuum to cure and obtain polyurethane damping material.

[0103] Comparative Example 3 1) Dissolve 30.6 g of 2,2'-dithiodibenzoic acid in 200 g of DMSO; then add 50.01 g of diphenylmethane diisocyanate and 0.2 g of dibutyltin dilaurate, and stir the mixture for 4 h under nitrogen protection.

[0104] 2) After the reaction is complete, the DMSO in the solution is removed by rotary evaporation to obtain the modified isocyanate resin.

[0105] 3) Weigh 100 parts of modified isocyanate resin, add 0.7 parts of dibutyltin dilaurate and 30 parts of diluent, stir evenly to obtain component B.

[0106] 4) Weigh 50 parts of polytetrahydrofuran-650 and place it in a slurry tank. Dry it in a vacuum oven at 100°C for 2 hours. While stirring at high speed (300 rpm), add 0.5 parts of defoamer BYK-LP D24043, 0.5 parts of wetting and dispersing agent BYK-2205, 1.5 parts of leveling agent BYK-399, 1 part of inorganic bentonite, 4 parts of aluminum tripolyphosphate, 5 parts of precipitated barium sulfate, 10 parts of basalt, 10 parts of heavy calcium carbonate, 15 parts of zinc phosphate, 15 parts of mica powder, and 30 parts of diluent to the slurry tank in sequence. Stir evenly, grind to a fineness of 80 μm using a three-roll mill, filter, and obtain component A.

[0107] 5) Weigh out component B and component B according to the ratio of n(OH):n(NCO)=1:1.04, mix them evenly, and obtain a polyurethane coating with self-healing function.

[0108] 6) Apply the self-healing polyurethane coating to a dry film thickness of 200μm and cure at 70℃ for 24 hours to obtain a self-healing polyurethane coating.

[0109] Comparative Example 4 1) Dissolve 15.82 g of 4,5-diamino-2-thiouracil in 200 g of DMSO; then add 50.01 g of diphenylmethane diisocyanate and 0.2 g of dibutyltin dilaurate, and stir the mixture for 4 h under nitrogen protection.

[0110] 2) After the reaction is complete, the DMSO in the solution is removed by rotary evaporation to obtain the modified isocyanate resin.

[0111] 3) Weigh 100 parts of modified isocyanate resin, add 0.7 parts of dibutyltin dilaurate and 30 parts of diluent, stir evenly to obtain component B.

[0112] 4) Weigh 50 parts of polytetrahydrofuran-650 and place it in a slurry tank. Dry it in a vacuum oven at 100°C for 2 hours. While stirring at high speed (300 rpm), add 0.5 parts of defoamer BYK-LP D24043, 0.5 parts of wetting and dispersing agent BYK-2205, 1.5 parts of leveling agent BYK-399, 1 part of inorganic bentonite, 4 parts of aluminum tripolyphosphate, 5 parts of precipitated barium sulfate, 10 parts of basalt, 10 parts of heavy calcium carbonate, 15 parts of zinc phosphate, 15 parts of mica powder, and 30 parts of diluent to the slurry tank in sequence. Stir evenly, grind to a fineness of 80 μm using a three-roll mill, filter, and obtain component A.

[0113] 5) Weigh out component B and component B according to the ratio of n(OH):n(NCO)=1:1.04, mix them evenly, and obtain a polyurethane coating with self-healing function.

[0114] 6) Apply the self-healing polyurethane coating to a dry film thickness of 200μm and cure at 70℃ for 24 hours to obtain a self-healing polyurethane coating.

[0115] Comparative Example 5 1) Weigh 15.32 g of 2,2'-dithiodibenzoic acid and 15.82 g of 4,5-diamino-2-thiouracil and dissolve them in 200 g of DMSO; then add 50.01 g of diphenylmethane diisocyanate, 0.2 g of dibutyltin dilaurate, 20.6 g of DCC and 0.61 g of DMAP, and stir the mixture for 4 h under nitrogen protection.

[0116] 2) After the reaction is complete, remove the insoluble matter in the solution by vacuum filtration; add 5 ml of dilute hydrochloric acid with pH=3 and stir for 30 minutes; then add 20 g of 4 Å molecular sieve, stir for 30 minutes and filter, remove DMSO in the filtrate by rotary evaporation to obtain modified isocyanate resin.

[0117] 3) Weigh 100 parts of modified isocyanate resin, add 0.7 parts of dibutyltin dilaurate and 30 parts of diluent, stir evenly to obtain component B.

[0118] 4) Weigh 50 parts of polytetrahydrofuran-650 and place it in a slurry tank. Dry it in a vacuum oven at 100°C for 2 hours. While stirring at high speed (300 rpm), add 0.5 parts of defoamer BYK-LP D24043, 0.5 parts of wetting and dispersing agent BYK-2205, 1.5 parts of leveling agent BYK-399, 1 part of inorganic bentonite, 4 parts of aluminum tripolyphosphate, 5 parts of precipitated barium sulfate, 10 parts of basalt, 10 parts of heavy calcium carbonate, 15 parts of zinc phosphate, 15 parts of mica powder, and 30 parts of diluent to the slurry tank in sequence. Stir evenly, grind to a fineness of 80 μm using a three-roll mill, filter, and obtain component A.

[0119] 5) Weigh out component B and component B according to the ratio of n(OH):n(NCO)=1:1.04, mix them evenly, and obtain a polyurethane coating with self-healing function.

[0120] 6) Apply the self-healing polyurethane coating to a dry film thickness of 200μm and cure at 70℃ for 24 hours to obtain a self-healing polyurethane coating.

[0121] Performance testing (a) Self-healing performance According to GB / T 16777-2008, the self-healing performance of the samples was tested using stress as the standard. Dumbbell-shaped samples were prepared from the self-healing polyurethane coatings prepared in Examples 1-4, the polyurethane elastomer prepared in Comparative Example 1, the polyurethane damping material prepared in Comparative Example 2, and the self-healing polyurethane coatings prepared in Comparative Examples 3-5, and their mechanical properties were tested. After cutting the samples, the cut surfaces were pressed together and placed in an oven at 80°C. After 24 hours, they were removed, cooled, and then their mechanical properties were tested. Each sample was tested three times, and the average value was taken, as shown in Table 1. In Table 1, self-healing efficiency = stress. (修复后) / stress.

[0122] (ii) Salt spray resistance According to GB / T 10125-2021, the neutral salt spray resistance of the samples was tested using a 3.5 wt% sodium chloride aqueous solution. The test results are shown in Table 2.

[0123] (III) Damping performance The dynamic thermomechanical properties of the coating were tested using a mechanical thermal analyzer, and the damping performance of the sample was evaluated by the magnitude of the damping loss factor. The test results are shown in Table 3.

[0124] Table 1

[0125] Table 2

[0126] Table 3

[0127] Table 1 shows that the self-healing polyurethane coatings prepared in Examples 1-4 have a self-healing efficiency of over 82.61%, reaching as high as 98.07%, which is far higher than the self-healing efficiency (57.5%-69.8%) of existing self-healing polyurethane coatings (Comparative Examples 1-2). This indicates that the self-healing polyurethane coatings provided by this invention have excellent self-healing performance.

[0128] The difference between Example 4 and Comparative Examples 3 and 4 lies in the substances used to modify the diisocyanate. Example 4 uses the reaction product of 2,2'-dithiobenzoic acid and 4,5-diamino-2-thiouracil to modify the diisocyanate, while Comparative Examples 3 and 4 use 2,2'-dithiobenzoic acid and 4,5-diamino-2-thiouracil, respectively, to modify the diisocyanate. Compared with Comparative Examples 3 and 4, the self-healing efficiency of Example 4 increased by 12.24% and 21.21%, respectively. This indicates that, compared to using disulfide chain extenders and polyhydrogen-bonded pyrimidines alone to modify diisocyanate, using the reaction product of both can further improve the self-healing performance of the coating.

[0129] The difference between Example 4 and Comparative Example 5 lies in the different steps used to prepare the modified isocyanate. In Example 4, 2,2'-dithiobenzoic acid and 4,5-diamino-2-thiouracil were reacted first before being modified with diisocyanate. In Comparative Example 5, 2,2'-dithiobenzoic acid, 4,5-diamino-2-thiouracil, and diisocyanate were reacted directly. Compared with Comparative Example 5, the self-healing efficiency of Example 4 was increased by 21.67%. This indicates that, under the condition that diisocyanate is modified using disulfide chain extenders and polyhydrogen-bonded pyrimidines, changing the reaction steps so that the disulfide chain extenders and polyhydrogen-bonded pyrimidines react first can further improve the self-healing performance of the coating.

[0130] The difference between Examples 1-2 and Examples 3-4 lies in the selection of disulfide chain extender, polyhydrogen-bonded pyrimidine, and diisocyanate. Compared with Examples 3-4, the self-healing efficiency of Examples 1-2 increased by 10.54%-15.46%. This indicates that the use of dithioglycolic acid and 2-amino-4-hydroxy-6-methylpyrimidine to modify hexamethylene diisocyanate, and 3,3'-dithiodipropionic acid and 4-amino-6-hydroxy-2-mercaptopyrimidine to modify isophorone diisocyanate, can further improve the self-healing performance of the coating.

[0131] Table 2 shows that the self-healing polyurethane coatings prepared in Examples 1-4 showed no change in their resistance to neutral salt spray (300h), while the self-healing polyurethane coatings (existing coatings) prepared in Comparative Examples 1-2 cracked and peeled off under the same conditions (300h). This indicates that the self-healing polyurethane coating provided by this invention has excellent salt spray resistance, and its salt spray resistance is significantly improved compared to existing self-healing polyurethane coatings.

[0132] Table 3 shows that the damping performance of Example 4 is superior to that of Comparative Examples 3-4. This indicates that, compared to modifying diisocyanate using disulfide chain extenders and polyhydrobonded pyrimidines alone, using the reaction products of both to modify diisocyanate can further improve the damping performance of the coating; under the condition that diisocyanate is modified using disulfide chain extenders and polyhydrobonded pyrimidines, changing the reaction steps so that the disulfide chain extenders and polyhydrobonded pyrimidines react first can further improve the damping performance of the coating.

Claims

1. A modified isocyanate resin having the chemical formula: OCN-R3-NHCO-O-R1-NHCO-R2-CONH-R1-O-CONH-R3-NCO; in, O-R1-NH is derived from polyhydrobonded pyrimidines; CO-R2-CO is derived from a disulfide chain extender containing two carboxyl groups; CONH-R3-NCO is derived from diisocyanate.

2. The modified isocyanate resin according to claim 1, characterized in that, The polyhydrogen-bonded pyrimidine is selected from , , , At least one of them; or / and, The disulfide chain extender is selected from... , , , At least one of them; or / and, The diisocyanate is selected from , , , At least one of them.

3. The modified isocyanate resin according to claim 1, characterized in that, It is obtained by reacting polyhydrogen-bonded pyrimidines, disulfide chain extenders, and diisocyanates.

4. A method for preparing the modified isocyanate resin according to any one of claims 1-3, comprising: The disulfide chain extender undergoes an amidation reaction with the polyhydrogen-bonded pyrimidine to generate a modified chain extender; The modified chain extender reacts with diisocyanate to undergo a carbamate reaction, thereby generating the modified isocyanate resin.

5. The preparation method according to claim 4, characterized in that, Includes the following steps: 1) Dissolve disulfide chain extender and polyhydrogen-bonded pyrimidine in a solvent, add catalyst A, and stir the reaction under an inert atmosphere; 2) After the reaction is complete, filter the solution, add dilute hydrochloric acid to the filtrate, then add molecular sieves, stir, filter again, and collect the filtrate. 3) Add diisocyanate and catalyst B to the filtrate and stir the reaction under an inert atmosphere; 4) After the reaction is complete, remove the solvent to obtain the modified isocyanate resin.

6. The preparation method according to claim 5, characterized in that, The solvent is selected from at least one of dimethyl sulfoxide, dichloromethane, xylene, and butyl acetate; or / and, The catalyst A is composed of dicyclohexylcarbodiimide and 4-N,N-dimethylpyridine; or / and The molecular sieve is selected from 4Å or 5Å molecular sieves; or / and The catalyst B is selected from dibutyltin dilaurate; or / and The inert atmosphere is a nitrogen atmosphere.

7. The preparation method according to claim 5, characterized in that, The molar ratio of the disulfide chain extender to the DCC is 1:1.5~2.5; or / and, The molar ratio of the disulfide chain extender to the DMAP is 1:0.12~0.18; or / and, The mass ratio of the diisocyanate to the catalyst B is 1:0.001~0.

01.

8. A self-healing polyurethane anti-corrosion damping coating, comprising component A and component B; Component A contains polytetrahydrofuran resin, pigments, fillers, additives, and diluent A; Component B contains isocyanate resin, catalyst C, and diluent B; The molar ratio of OH in component A to NCO in component B is 1:1.02~1.06; The isocyanate resin is selected from the modified isocyanate resin according to any one of claims 1-3 or the modified isocyanate resin prepared by the preparation method according to any one of claims 4-7. Preferably, In component A, by weight, there are 100 parts of polytetrahydrofuran resin, 20-100 parts of pigments and fillers, 1-10 parts of additives, and 10-70 parts of diluent A. In component B, by weight, there are 100 parts of isocyanate resin, 0.5-2 parts of catalyst C, and 10-50 parts of diluent B.

9. A self-healing polyurethane anti-corrosion damping coating as described in claim 8, characterized in that, The number-average molecular weight of the polytetrahydrofuran resin is less than or equal to 2000; or / and, The additive is selected from at least one of wetting and dispersing agents, defoamers, and leveling agents; or / and, The diluent A is selected from at least one of benzene-based diluents, ketone-based diluents, and ester-based diluents; or / and, The diluent B is selected from at least one of benzene-based diluents, ketone-based diluents, and ester-based diluents; or / and, The catalyst C is selected from at least one of dibutyltin dilaurate and stannous octoate; The pigments and fillers are selected from at least one of talc, heavy calcium carbonate, mica powder, iron oxide red, aluminum tripolyphosphate, basalt, zinc phosphate, precipitated barium sulfate, and bentonite.

10. A method for preparing a self-healing polyurethane anti-corrosion damping coating as described in claim 8 or 9, comprising: 1) Add additives and diluent A to polytetrahydrofuran resin, disperse evenly, add filler, disperse evenly, and obtain component A; 2) Mix the isocyanate resin, catalyst C, and diluent evenly to obtain component B; 3) After mixing component A and component B evenly according to the ratio, the self-healing polyurethane anti-corrosion damping coating is obtained.

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