Self-repairing, self-cleaning weather-resistant iron fender plate bottom integrated coating and preparation method thereof

Abstract

This invention belongs to the field of coating technology and proposes a self-healing, self-cleaning, weather-resistant coating for the bottom surface of iron pads and its preparation method. The coating is composed of component A and component B mixed in a ratio of 1-1.1 isocyanate index. Component A, by mass parts, comprises: 26-31 parts polyaspartic acid ester PAE-1, 26-29 parts polyaspartic acid ester PAE-2, 4-8 parts polyaspartic acid ester PAE-3, and 3-5 parts... The composition comprises: mica powder, 1-3 parts wetting and dispersing agent, 0.5-1 parts defoamer, 0.3-0.6 parts leveling agent, 0-3 parts color paste, 2-4 parts anti-settling agent, 5-8 parts ultraviolet absorber, 13.2-24.9 parts zinc phosphate, and 1-4 parts barium sulfate; Component B includes 7-12 parts isocyanate prepolymer A, 16-22 parts isocyanate prepolymer B, 65-75 parts hexamethylene diisocyanate trimer, and 2-4 parts butyl acetate. This technical solution solves the problem of insufficient salt spray resistance and weather resistance in existing polyaspartic ester polyurea coatings.

Description

Technical Field

[0001] This invention belongs to the field of coating technology and relates to a self-healing, self-cleaning, weather-resistant coating for the bottom surface of iron pads and its preparation method. Background Technology

[0002] With the rapid development of my country's high-speed railway industry and the increasing demands for extended protection lifespan, improving the applicability of track components, elastic clips, and rail pads in various environments has become a major concern. These components are exposed to harsh environments such as humidity, salt spray, ultraviolet radiation, and thermal shock for extended periods, and traditional protection systems are gradually becoming insufficient to meet the needs of long-term protection. Currently, high-speed rail metal corrosion protection includes epoxy zinc-rich primer, intermediate layer, and topcoat. Among them, epoxy zinc-rich primer has high adhesion to the substrate and improves the salt spray resistance of the paint film through cathodic protection. The intermediate layer increases the paint film thickness and provides waterproofing. The topcoat is usually an acrylic polyurethane coating with excellent weather resistance. Although this system is widely used, it has several inherent drawbacks: First, the system requires multiple application steps, which are complex, have a long construction cycle, and are inefficient; second, the solvent-based epoxy and polyurethane coatings contain a large amount of volatile organic compounds (VOCs), which do not meet increasingly stringent environmental regulations; third, the zinc powder in epoxy zinc-rich primer also poses environmental and health risks during production and use.

[0003] With increasing environmental awareness, oil-based paints are gradually being replaced by water-based paints. However, water-based paints have significant limitations: their film-forming process is extremely sensitive to environmental temperature and humidity; they cure slowly and have poor film-forming properties at low temperatures; and in high humidity environments, moisture is difficult to evaporate, easily leading to problems such as blistering and defects in the paint film, seriously affecting the final protective effect. Furthermore, water-based paints are usually difficult to apply thickly in one coat, requiring multiple applications to achieve the specified film thickness, which also affects application efficiency.

[0004] Polyaspartic acid ester polyurea, as a third-generation polyurea, boasts advantages such as environmental friendliness, adjustable curing speed, minimal environmental impact, low-temperature curing capability, and no need for baking. It also offers energy savings and emission reduction to some extent, high film thickness, and strong adhesion, allowing for one-step film formation to replace water-based coatings. However, existing ordinary polyaspartic acid esters still have two major performance shortcomings: firstly, poor hydrophobicity and poor salt spray resistance after abrasion, making it incomparable to epoxy zinc-rich primers; secondly, its weather resistance lags behind that of acrylic polyurethane topcoats.

[0005] Chinese patent CN 119552562 A discloses a composite coating based on modified polyaspartic acid ester. This composite coating includes a base coat, a middle coat, and a top coat. The base coat comprises a specific silicone-modified polyaspartic acid ester primer resin; the middle coat comprises a specific polyaspartic acid ester intermediate coat resin; and the top coat comprises a specific imide-modified polyaspartic acid ester top coat resin. The base coat is applied to the substrate and cured to form a high-adhesion, high-penetration, and moisture-proof base layer. Then, the middle coat is applied and cured on top of the base coat to form a high-compression-strength, high-elasticity, solvent-free intermediate coat. The cured intermediate coat surface is then sanded to improve adhesion. Finally, the aforementioned top coat is applied on top of the intermediate coat to form a highly wear-resistant, solvent-free top coat. This coating is a composite system comprising base, middle, and top layers. This requires multiple construction steps, different mixing systems, a long construction period, high cost, and higher technical requirements for construction personnel.

[0006] For example, Chinese patent application CN 114958164 A discloses a two-component polyurea-modified waterproof coating and its preparation method. The coating consists of component A and component B. Component B, by weight, includes: 50-60 parts of polyaspartic acid ester, 10-12 parts of an anti-aging agent, 2-3 parts of an adhesion promoter, 0.5-0.7 parts of a defoamer, and 1.5-2 parts of a leveling agent. This waterproof coating uses a two-component polyurea as a matrix, and an anti-aging agent is added to modify the coating. The anti-aging agent is nano-SiO2 with surface-grafted organic molecular chains, which promotes the uniform dispersion of nano-SiO2 in the coating, thereby improving the coating's resistance to UV aging and thermal aging. Furthermore, the surface-grafted organic molecular chains include phenylpropane and benzoic acid ester structures, both of which have certain UV shielding functions, thus achieving the purpose of anti-UV aging at the chemical level. The anti-aging agent is surface-grafted organic molecular chains of nano-SiO2, which is a physical addition method. Nanoparticles are prone to agglomeration and sedimentation during long-term storage and curing in coatings, leading to uneven and unstable performance.

[0007] Chinese patent CN 120209691 A discloses a method for preparing a bio-based polyurea coating resin with high wear resistance and fluorine-free antifouling properties. This method uses interpenetrating network polymerization (IPN) to lock polydimethylsiloxane within a polyurea matrix, combining it with bio-based raw materials such as castor oil and benzene-free isocyanates to prepare an environmentally friendly coating. Specific steps include prepolymer preparation, mixing of polyaspartic acid ester and PDMS, vacuum degassing, and curing. The resulting coating is free of fluorine compounds and volatile organic solvents, and possesses high hydrophobicity, wear resistance, and excellent mechanical properties. This method uses IPN technology to physically lock PDMS to provide hydrophobicity. However, under long-term mechanical wear and aging, PDMS segments may gradually migrate and be lost, leading to a gradual decrease in antifouling and hydrophobic properties. Furthermore, its protection is passive, relying on the hydrophobic surface to prevent dirt adhesion. Once the coating is scratched or damaged, its protective function fails and it cannot self-repair.

[0008] Therefore, there is an urgent need to develop a new type of coating that can inherit the advantages of polyaspartic ester polyurea, such as environmental friendliness and convenient construction, while fundamentally overcoming its shortcomings in protective properties such as salt spray resistance and weather resistance. This application arose against this background. Summary of the Invention

[0009] This invention proposes a self-healing, self-cleaning, weather-resistant coating for the bottom surface of iron pads and its preparation method, which solves the problems of insufficient salt spray resistance and weather resistance of polyaspartic acid ester polyurea coatings in the prior art.

[0010] The technical solution of this invention is implemented as follows:

[0011] A self-healing, self-cleaning, weather-resistant coating for the bottom surface of iron pads is composed of component A and component B mixed in a ratio of isocyanate index of 1 to 1.1. Component A, by mass parts, comprises: 26 to 31 parts polyaspartic acid ester PAE-1, 26 to 29 parts polyaspartic acid ester PAE-2, 4 to 8 parts polyaspartic acid ester PAE-3, 3 to 5 parts mica powder, 1 to 3 parts wetting and dispersing agent, 0.5 to 1 part defoamer, 0.3 to 0.6 parts leveling agent, 0 to 3 parts color paste, 2 to 4 parts anti-settling agent, 5 to 8 parts ultraviolet absorber, 13.2 to 24.9 parts zinc phosphate, and 1 to 4 parts barium sulfate. Component B comprises 7-12 parts isocyanate prepolymer A, 16-22 parts isocyanate prepolymer B, 65-75 parts hexamethylene diisocyanate trimer, and 2-4 parts butyl acetate; the polyaspartic ester PAE-1 is a polyaspartic ester containing polydimethylsiloxane segments; the polyaspartic ester PAE-2 is a polyaspartic ester containing disulfide bonds; and the polyaspartic ester PAE-3 is a polyaspartic ester containing disulfide bonds and silane coupling groups.

[0012] Preferably, the polyaspartic acid ester PAE-1 is obtained by esterification of maleic anhydride and n-octanol, followed by Michael addition reaction of the esterification product with diaminopropyl polydimethylsiloxane.

[0013] Preferably, the polyaspartic acid ester PAE-2 is obtained by esterification of maleic anhydride with 2,2'-dithiodiethanol and n-octanol, followed by Michael addition reaction of the esterification product with cyclohexylmethylamine.

[0014] Preferably, the polyaspartic acid ester PAE-3 is obtained by esterification of maleic anhydride with 2,2'-dithiodiethanol and n-octanol, followed by Michael addition reaction of the esterification product with γ-aminopropyltriethoxysilane.

[0015] The color paste is a commonly used colorant in the coatings industry, and its dosage is 0-3 parts, preferably 2-3 parts. The addition of color paste is mainly to meet decorative or marking requirements. Those skilled in the art should understand that variations in the type of color paste (such as black, white, gray, etc.) and its dosage within the range of 0-3 parts will not have a substantial impact on the key properties of the coating of this invention, such as salt spray resistance and weather resistance. Those skilled in the art can choose whether to add color paste, and the type and specific dosage of color paste added, according to actual needs.

[0016] Preferably, the raw materials of the polyaspartic acid ester PAE-1 include the following components in parts by weight: 6.5 to 7.8 parts maleic anhydride, 17.5 to 21.5 parts n-octanol and 70.5 to 75.7 parts diaminopropyl polydimethylsiloxane.

[0017] Preferably, the raw materials of the polyaspartic acid ester PAE-1 include the following components in parts by weight: 7.2 parts maleic anhydride, 19.2 parts n-octanol and 73.6 parts diaminopropyl polydimethylsiloxane.

[0018] Preferably, the preparation method of the polyaspartic acid ester PAE-1 includes the following steps:

[0019] Maleic anhydride and n-octanol were mixed and reacted at 40-45℃ for 1.5-2 hours. The temperature was then raised to 180-200℃, and the water generated was removed under reduced pressure. The vacuum was maintained at -0.05 to -0.06 MPa, and the reaction was continued for 1.5-2.5 hours. The vacuum was then increased to -0.09 MPa to -0.095 MPa, and the mixture was heated for 2-3 hours. Heating was stopped when the acid value dropped below 3 mg KOH / g. When the temperature dropped below 30℃, diaminopropyl polydimethylsiloxane was added dropwise, and the mixture was reacted at 40-45℃ for 2.5-3 hours. The temperature was then raised to 105-110℃ and the reaction was continued for 4-5 hours to obtain polyaspartic acid ester PAE-1.

[0020] Preferably, the molecular weight of the diaminopropyl polydimethylsiloxane is 1800~2200 g / mol, more preferably 2000 g / mol.

[0021] Preferably, the raw materials of the polyaspartic acid ester PAE-2 include the following components in parts by weight: 22.5-24.6 parts maleic anhydride, 17.6-18.9 parts 2,2'-dithiodiethanol, 30.3-33.1 parts n-octanol and 25.7-28.3 parts cyclohexylmethylamine.

[0022] Preferably, the raw materials of the polyaspartic acid ester PAE-2 include the following components in parts by weight: 23.5 parts maleic anhydride, 18.2 parts 2,2'-dithiodiethanol, 31.2 parts n-octanol and 27.1 parts cyclohexylmethylamine.

[0023] Preferably, the preparation method of the polyaspartic acid ester PAE-2 includes the following steps:

[0024] Maleic anhydride and 2,2'-dithiodiethanol were mixed and heated to 75-85℃ for 2-2.5 h. Then, n-octanol was added, and the temperature was raised to 180-200℃. The water generated was removed under reduced pressure, and the vacuum was maintained at -0.05 to -0.06 MPa for 1.5-2.5 h. The vacuum was then increased to -0.09 MPa to -0.095 MPa and heated for 2-3 h. Heating was stopped when the acid value dropped below 3 mg KOH / g. When the temperature dropped below 30℃, cyclohexylmethylamine was added dropwise, and the temperature was raised to 105-110℃ for 3.5-4.5 h to obtain polyaspartic acid ester PAE-2.

[0025] Preferably, the raw materials of the polyaspartic acid ester PAE-3 include the following components in parts by weight: 17.4-19.8 parts maleic anhydride, 13.7-15.1 parts 2,2'-dithiodiethanol, 22.9-25.7 parts n-octanol and 40.9-43.6 parts γ-aminopropyltriethoxysilane.

[0026] Preferably, the raw materials of the polyaspartic acid ester PAE-3 include the following components in parts by weight: 18.6 parts maleic anhydride, 14.5 parts 2,2'-dithiodiethanol, 24.8 parts n-octanol and 42.1 parts γ-aminopropyltriethoxysilane.

[0027] Preferably, the preparation method of the polyaspartic acid ester PAE-3 includes the following steps:

[0028] Maleic anhydride and 2,2'-dithiodiethanol were mixed and heated to 75-85℃ for 2-2.5 h. Then, n-octanol was added and the temperature was raised to 180-200℃ to remove the generated water under reduced pressure. The vacuum was maintained at -0.05 to -0.06 MPa and the reaction was continued for 1.5-2.5 h. The vacuum was then increased to -0.09 MPa to -0.095 MPa and the mixture was heated for 2-3 h. Heating was stopped when the acid value dropped below 3 mg KOH / g. When the temperature dropped below 30℃, γ-aminopropyltriethoxysilane was added dropwise and the temperature was raised to 115-120℃ for 3.5-4.5 h to obtain polyaspartic acid ester PAE-3.

[0029] Preferably, the ultraviolet absorber is selected from at least one of ultraviolet absorbers UV-327, UV-326, UV-328, and UV-531. More preferably, the ultraviolet absorber is a reactive ultraviolet absorber, obtained by ring-opening esterification of 3-[3-(2-H-benzotriazol-2-yl)-4-hydroxy-5-tert-butylphenyl]-propionic acid and octyl glycidyl ether in the presence of a catalyst.

[0030] Preferably, the reactive ultraviolet absorber is prepared from 62-68 parts of 3-[3-(2-H-benzotriazol-2-yl)-4-hydroxy-5-tert-butylphenyl]-propionic acid, 31-37 parts of octyl glycidyl ether and 0.5-1.5 parts of triphenylphosphine.

[0031] Preferably, the reactive ultraviolet absorber is prepared from 65 parts of 3-[3-(2-H-benzotriazol-2-yl)-4-hydroxy-5-tert-butylphenyl]-propionic acid, 34 parts of octyl glycidyl ether and 1 part of triphenylphosphine.

[0032] Preferably, the preparation method of the reactive ultraviolet absorber includes the following steps:

[0033] 3-[3-(2-H-benzotriazol-2-yl)-4-hydroxy-5-tert-butylphenyl]-propionic acid, octyl glycidyl ether, and triphenylphosphine were mixed and heated to 110-120℃. The reaction was carried out for 5-6 hours. Heating was stopped when the acid value dropped to 20 mg KOH / g to obtain a reactive ultraviolet absorber.

[0034] Preferably, the particle size of the mica powder is 800 mesh to 1250 mesh.

[0035] Preferably, the mica powder has a particle size of 1250 mesh.

[0036] Preferably, the defoamer is selected from one or more of BYK-054T, BYK-085, BYK-088, Airex920 and Airex990, or a mixture thereof.

[0037] Preferably, the leveling agent is selected from one or more of BYK-310, BYK-UV 3505, TEGO GLIDE450, and TEGO GLIDE496, or a mixture thereof.

[0038] The anti-settling agent is selected from one or more of BYK-410, organic modified bentonite BENGEL 828, and fumed silica R8200, or a mixture thereof.

[0039] Preferably, the wetting and dispersing agent is selected from one or more of DISPERS750W, DISPERS740W, and ANTI-TERRA-U100, or a mixture thereof.

[0040] Preferably, the hexamethylene diisocyanate trimer is HT-100 and / or HT-300.

[0041] Preferably, the isocyanate prepolymer A is polymerized from isophorone diisocyanate and trimethylolpropane under the action of a catalyst; and the isocyanate prepolymer B is polymerized from isophorone diisocyanate and polytetrahydrofuran ether diol under the action of a catalyst.

[0042] Preferably, the isocyanate prepolymer A is prepared from 87-92 parts of isophorone diisocyanate, 9-11 parts of trimethylolpropane and 0.05-0.15 parts of catalyst.

[0043] Preferably, the isocyanate prepolymer A is prepared from 89.2 parts of isophorone diisocyanate, 10.7 parts of trimethylolpropane and 0.1 parts of catalyst.

[0044] Preferably, the method for preparing isocyanate prepolymer A includes the following steps:

[0045] Isophorone diisocyanate, trimethylolpropane and catalyst were mixed and kept at 35~45℃ for 2.5~3.5h to obtain isocyanate prepolymer A.

[0046] Preferably, the isocyanate prepolymer B is prepared from 29-33 parts of isophorone diisocyanate, 66.8-70.5 parts of polytetrahydrofuran ether diol 1000 and 0.05-0.15 parts of catalyst.

[0047] Preferably, the isocyanate prepolymer B is prepared from 30.8 parts of isophorone diisocyanate, 69.1 parts of polytetrahydrofuran ether diol 1000 and 0.1 parts of catalyst.

[0048] Preferably, the method for preparing isocyanate prepolymer B includes the following steps:

[0049] Isophorone diisocyanate, polytetrahydrofuran ether diol 1000 and catalyst were mixed and kept at 85~95℃ for 2.5~3.5h. Heating was then stopped to obtain isocyanate prepolymer B.

[0050] Preferably, the catalysts in both isocyanate prepolymer A and isocyanate prepolymer B are H05, H09, or PC-02.

[0051] Technical Theme Two

[0052] The preparation method of the self-healing, self-cleaning, weather-resistant iron pad bottom surface integrated coating as described in Technical Topic 1 above includes the following steps:

[0053] S1. Preparation of Component A

[0054] Polyaspartic acid ester PAE-1, polyaspartic acid ester PAE-2, polyaspartic acid ester PAE-3, mica powder, wetting and dispersing agent, defoamer, reactive ultraviolet absorber, zinc phosphate and barium sulfate are mixed and dispersed, then ground to a fineness ≤15um, and then leveling agent, color paste and anti-settling agent are added, stirred and mixed, and stored in a sealed container to obtain component A;

[0055] Preparation of S2.B component

[0056] Isocyanate prepolymer A, isocyanate prepolymer B, hexamethylene diisocyanate trimer and butyl acetate were mixed and stirred to obtain component B;

[0057] S3. Mix components A and B.

[0058] Preferably, the preparation of component A in step S1 includes the following steps:

[0059] Polyaspartic acid ester PAE-1, polyaspartic acid ester PAE-2, polyaspartic acid ester PAE-3, mica powder, wetting and dispersing agent, defoamer, reactive ultraviolet absorber, zinc phosphate, and barium sulfate were mixed and dispersed at a stirring speed of 700-800 rpm for 20-30 min. Then, the mixture was ground to a fineness ≤15 μm. Leveling agent, black paste, and anti-settling agent were added, and the mixture was stirred at a stirring speed of 800-900 rpm for 15-20 min. The mixture was then sealed and stored to obtain component A.

[0060] Preferably, the preparation of component B in step S2 includes the following steps:

[0061] Isocyanate prepolymer A, isocyanate prepolymer B, hexamethylene diisocyanate trimer, and butyl acetate were mixed and stirred at a speed of 60-80 r / min for 30-45 min to obtain component B.

[0062] Preferably, the stirring speed in step S3 is 300~350 r / min, and the mixing time is 20~25 min.

[0063] The beneficial effects of the present invention using the above technical solution are as follows:

[0064] 1. In this invention, component A, containing a secondary amine, reacts rapidly with component B, which contains isocyanate, and has a high solids content. Therefore, a single spray coat meets the required film thickness. The coating does not require heating for curing at low temperatures, improving production efficiency. No bubbles appear on the surface under humid conditions, and the coating's protective performance against iron parts is unaffected. This invention achieves the core protective goals of the traditional three-layer system (primer, intermediate coat, and topcoat) by using polyaspartic acid ester PAE-1, polyaspartic acid ester PAE-2, and polyaspartic acid ester PAE-3 synergistically, i.e., a single spray coating. The polyaspartic acid ester PAE-1, prepared using long-chain alkyl alcohols and diaminopropyl polydimethylsiloxane, not only possesses strong hydrophobicity, improving the coating's resistance to damp heat and salt spray, but also benefits from the long-chain alkyl groups protecting the main chain, and the high silicon-oxygen bond energy enhances the overall weather resistance of the coating.

[0065] 2. In this invention, 2,2'-dithiodiethanol is used to prepare polyaspartic acid ester PAE-2 and polyaspartic acid ester PAE-3. The disulfide bond can play a self-healing role. After the paint film is damaged, it can self-repair at room temperature. Heating or light exposure can improve the self-healing speed.

[0066] 3. In the preparation of polyaspartic acid ester PAE-3 of the present invention, a silane coupling agent is added. After hydrolysis, the silanol groups react with the metal surface, which improves the adhesion of the substrate. Therefore, the paint film has excellent salt spray resistance.

[0067] 4. The present invention uses a reactive ultraviolet absorber, which can be better dissolved in the system. At the same time, the reactive ultraviolet absorber has multiple ring structures that can block water vapor and improve adhesion. It has a synergistic effect with the silane coupling agent, resulting in better salt spray resistance and ultraviolet resistance. Detailed Implementation

[0068] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0069] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. Unless otherwise specified, the experimental or testing methods involved in the embodiments of this invention are conventional methods in the prior art, and their names and / or abbreviations are conventional names in the art, clearly defined in their respective fields of application. Those skilled in the art can understand the conventional process steps based on these names and apply the corresponding equipment, implementing them under conventional conditions or conditions recommended by the manufacturer. The various instruments, equipment, raw materials, or reagents used in the embodiments of this invention are not subject to any special restrictions on their source; they are all conventional products that can be purchased through legitimate commercial channels and can be prepared according to conventional methods well known to those skilled in the art.

[0070] In the preparation of polyaspartic acid ester PAE-1, diaminopropyl polydimethylsiloxane with a molecular weight of 2000 g / mol was purchased from Hubei Langbowan Biomedical Co., Ltd.

[0071] The leveling agents BYK-310 and BYK-UV 3505 and the anti-settling additive BYK-410, brand name BYK Chemicals (Germany), were purchased from Hualing Coatings Co., Ltd.

[0072] The leveling agents TEGO GLIDE450 and TEGO GLIDE496 are manufactured by Evonik Degussa, Germany.

[0073] The leveling agent TEGO GLIDE 450 was purchased from Guangzhou Huiwangcheng Chemical Co., Ltd.

[0074] The leveling agent TEGO GLIDE496 was purchased from Shanghai Buding Chemical Co., Ltd.

[0075] Organically modified bentonite BENGEL 828 is produced by Haiming Sideqian Chemical Co., Ltd.

[0076] The grade of fumed silica R8200 is Evonik Degussa from Germany, purchased from Chengdu Jingyi New Materials Co., Ltd.

[0077] The wetting and dispersing agents DISPERS750W and DISPERS740W are manufactured by Evonik GmbH of Germany and purchased from Guangzhou Haoyi New Material Technology Co., Ltd.

[0078] ANTI-TERRA-U100 is manufactured by BYK GmbH in Germany and purchased from Guangzhou Siteyuan Chemical Co., Ltd.

[0079] Catalysts H05, H09, and PC-02 are all manufactured by Yantai Sunshine Rubber & Plastics Co., Ltd.

[0080] Zinc phosphate is designated as PZ20.

[0081] Barium sulfate is precipitated barium sulfate.

[0082] The black pigment is RAL 9005 Jet black. No pigment needs to be added when no decoration or marking is required; the protective properties of the coating will not be affected.

[0083] The particle size of the mica powder is 1250 mesh.

[0084] CAS No.: 1892-29-1, Molecular Weight: 154.25, EC No.: 217-576-6.

[0085] The vacuum levels described below are gauge pressures, based on local atmospheric pressure, and are negative.

[0086] Unless otherwise specified, all parts mentioned in this invention are parts by weight.

[0087] Preparation Example 1

[0088] The preparation method of polyaspartic acid ester PAE-1 includes the following steps:

[0089] 6.5 parts of maleic anhydride and 17.5 parts of n-octanol were added to a four-necked flask, and the temperature was gradually increased to 45°C and reacted for 1.5 h. The temperature was then increased to 200°C, and the water generated was removed under reduced pressure. The vacuum was maintained at -0.05 MPa, and the reaction was continued for 2.5 h. The vacuum was then increased to -0.09 MPa and heated for 3 h. Heating was stopped when the acid value dropped below 3 mg KOH / g. The temperature was then lowered to 30°C, and 70.5 parts of diaminopropyl polydimethylsiloxane were added dropwise. The reaction was continued at 45°C for 2.5 h, and then increased to 110°C and reacted for 4 h to obtain polyaspartic acid ester, named PAE-1-1.

[0090] Preparation Example 2

[0091] 7.2 parts of maleic anhydride and 19.2 parts of n-octanol were added to a four-necked flask, and the temperature was gradually increased to 40°C and reacted for 2 hours. The temperature was then increased to 180°C, and the water generated was removed under reduced pressure. The vacuum was maintained at -0.06 MPa, and the reaction was continued for 1.5 hours. The vacuum was then increased to -0.095 MPa and heated for 2 hours. Heating was stopped when the acid value dropped below 3 mg KOH / g. The temperature was then lowered to 30°C, and 73.6 parts of diaminopropyl polydimethylsiloxane were added dropwise. The reaction was continued at 45°C for 3 hours, and then increased to 105°C and reacted for 5 hours to obtain polyaspartic acid ester, named PAE-1-2.

[0092] Preparation Example 3

[0093] 7.8 parts of maleic anhydride and 21.5 parts of n-octanol were added to a four-necked flask, and the temperature was gradually increased to 45°C and reacted for 2 hours. The temperature was then increased to 190°C, and the water generated was removed under reduced pressure. The vacuum was maintained at -0.05 MPa, and the reaction was continued for 2 hours. The vacuum was increased to -0.09 MPa, and the reaction was continued for 2.5 hours. Heating was stopped when the acid value dropped below 3 mg KOH / g. The temperature was then lowered to 30°C, and 75.7 parts of diaminopropyl polydimethylsiloxane were added dropwise. The reaction was continued at 40°C for 3 hours, and then the temperature was increased to 110°C and the reaction was continued for 4.5 hours to obtain polyaspartic acid ester, named PAE-1-3.

[0094] Preparation Example 4

[0095] The preparation method of polyaspartic acid ester PAE-2 includes the following steps:

[0096] 22.5 parts of maleic anhydride and 17.6 parts of 2,2'-dithiodiethanol were added to a four-necked flask, and the temperature was gradually increased to 80°C and reacted for 2 hours. Then, 30.3 parts of n-octanol were added, and the temperature was increased to 190°C. The water generated was removed under reduced pressure, and the vacuum was maintained at -0.055 MPa for 2 hours. The vacuum was then increased to -0.09 MPa and the mixture was heated for 2.5 hours. Heating was stopped when the acid value dropped below 3 mg KOH / g. The temperature was lowered to 30°C, and 25.7 parts of cyclohexylmethylamine were added dropwise. The temperature was increased to 110°C and the mixture was reacted for 4 hours to obtain polyaspartic acid ester, named PAE-2-1.

[0097] Preparation Example 5

[0098] The preparation method of polyaspartic acid ester PAE-2 includes the following steps:

[0099] 23.5 parts of maleic anhydride and 18.2 parts of 2,2'-dithiodiethanol were added to a four-necked flask, and the temperature was gradually increased to 75°C and reacted for 2.5 h. Then, 31.2 parts of n-octanol were added, and the temperature was increased to 180°C. The water generated was removed under reduced pressure, and the vacuum was maintained at -0.06 MPa for 1.5 h. The vacuum was then increased to -0.095 MPa and heated for 2 h. Heating was stopped when the acid value dropped below 3 mg KOH / g. The temperature was lowered to 30°C, and 27.1 parts of cyclohexylmethylamine were added dropwise. The temperature was increased to 110°C and reacted for 3.5 h to obtain polyaspartic acid ester, named PAE-2-2.

[0100] Preparation Example 6

[0101] The preparation method of polyaspartic acid ester PAE-2 includes the following steps:

[0102] 24.6 parts of maleic anhydride and 18.9 parts of 2,2'-dithiodiethanol were added to a four-necked flask, and the temperature was gradually increased to 85°C and reacted for 2 hours. Then, 33.1 parts of n-octanol were added, and the temperature was increased to 200°C. The water generated was removed under reduced pressure, and the vacuum was maintained at -0.05 MPa for 2.5 hours. The vacuum was then increased to -0.09 MPa and the mixture was heated for 3 hours. Heating was stopped when the acid value dropped below 3 mg KOH / g. The temperature was lowered to 30°C, and 28.3 parts of cyclohexylmethylamine were added dropwise. The temperature was increased to 105°C and the mixture was reacted for 4.5 hours to obtain polyaspartic acid ester, named PAE-2-3.

[0103] Preparation Example 7

[0104] The preparation method of polyaspartic acid ester PAE-3 includes the following steps:

[0105] 17.4 parts of maleic anhydride and 13.7 parts of 2,2'-dithiodiethanol were added to a four-necked flask, and the temperature was gradually increased to 80°C and reacted for 2 hours. Then, 22.9 parts of n-octanol were added, and the temperature was increased to 190°C while reducing the pressure to remove the generated water. The vacuum was maintained at -0.055 MPa, and the reaction was continued for 2 hours. The vacuum was then increased to -0.09 MPa, and the mixture was heated for 2.5 hours. Heating was stopped when the acid value dropped below 3 mg KOH / g. The temperature was then lowered to 30°C, and 40.9 parts of γ-aminopropyltriethoxysilane were added dropwise. The temperature was increased to 115°C, and the reaction was continued for 4 hours to obtain polyaspartic acid ester, named PAE-3-1.

[0106] Preparation Example 8

[0107] The preparation method of polyaspartic acid ester PAE-3 includes the following steps:

[0108] 18.6 parts of maleic anhydride and 14.5 parts of 2,2'-dithiodiethanol were added to a four-necked flask, and the temperature was gradually increased to 75°C and reacted for 2.5 h. Then, 24.8 parts of n-octanol were added, and the temperature was increased to 180°C to remove the generated water under reduced pressure. The vacuum was maintained at -0.06 MPa, and the reaction was carried out for 1.5 h. The vacuum was then increased to -0.095 MPa and the mixture was heated for 2 h. Heating was stopped when the acid value dropped below 3 mg KOH / g. The temperature was lowered to 30°C, and 42.1 parts of γ-aminopropyltriethoxysilane were added dropwise. The temperature was increased to 120°C and the reaction was carried out for 3.5 h to obtain polyaspartic acid ester, named PAE-3-2.

[0109] Preparation Example 9

[0110] The preparation method of polyaspartic acid ester PAE-3 includes the following steps:

[0111] 19.8 parts of maleic anhydride and 15.1 parts of 2,2'-dithiodiethanol were added to a four-necked flask, and the temperature was gradually increased to 85°C and reacted for 2 hours. Then, 25.7 parts of n-octanol were added, and the temperature was increased to 200°C while reducing the pressure to remove the generated water. The vacuum was maintained at -0.05 MPa, and the reaction was carried out for 2.5 hours. The vacuum was then increased to -0.09 MPa and the reaction was continued for 3 hours. Heating was stopped when the acid value dropped below 3 mg KOH / g. The temperature was then lowered to 30°C, and 43.6 parts of γ-aminopropyltriethoxysilane were added dropwise. The temperature was increased to 115°C and the reaction was continued for 4.5 hours to obtain polyaspartic acid ester, named PAE-3-3.

[0112] Preparation Example 10

[0113] The preparation method of reactive ultraviolet absorbers includes the following steps:

[0114] 65 parts of 3-[3-(2-H-benzotriazol-2-yl)-4-hydroxy-5-tert-butylphenyl]-propionic acid, 34 parts of octyl glycidyl ether, and 1 part of triphenylphosphine were added to a four-necked flask. The temperature was gradually increased to 115°C, and the reaction was carried out for 5.5 hours. Heating was stopped when the acid value dropped to 20 mg KOH / g, and the reactive ultraviolet absorber was obtained and named RUVA-1.

[0115] Preparation Example 11

[0116] The preparation method of reactive ultraviolet absorbers includes the following steps:

[0117] 68 parts of 3-[3-(2-H-benzotriazol-2-yl)-4-hydroxy-5-tert-butylphenyl]-propionic acid, 37 parts of octyl glycidyl ether, and 1.5 parts of triphenylphosphine were added to a four-necked flask, and the temperature was gradually increased to 110°C. The reaction was carried out for 6 hours. Heating was stopped when the acid value dropped to 20 mg KOH / g, and the reactive ultraviolet absorber was obtained and named RUVA-2.

[0118] Preparation Example 12

[0119] The preparation method of reactive ultraviolet absorbers includes the following steps:

[0120] 62 parts of 3-[3-(2-H-benzotriazol-2-yl)-4-hydroxy-5-tert-butylphenyl]-propionic acid, 31 parts of octyl glycidyl ether, and 0.5 parts of triphenylphosphine were added to a four-necked flask, and the temperature was gradually increased to 120°C. The reaction was carried out for 5 hours. Heating was stopped when the acid value dropped to 20 mg KOH / g, and the reactive ultraviolet absorber was obtained and named RUVA-3.

[0121] The reactive UV absorber in component A contains reactive hydroxyl groups in its molecular structure. During the coating curing process, these hydroxyl groups participate in the cross-linking reaction with the isocyanate groups in component B. Therefore, when calculating the isocyanate index, the total number of moles of reactive groups in component A should be counted as the sum of the moles of amino groups in all polyaspartic esters and the moles of hydroxyl groups in the reactive UV absorber.

[0122] The hydroxyl content of the reactive ultraviolet absorber is characterized by its hydroxyl value or hydroxyl equivalent. Its hydroxyl value can be determined according to the national standard GB / T 12008.3-2009 "Plastics - Polyether Polyols - Part 3: Determination of Hydroxyl Value". Based on the measured hydroxyl value, its hydroxyl equivalent can be calculated. Similarly, the amino equivalent of the polyaspartic acid ester, and the isocyanate content of isocyanate prepolymer A and isocyanate prepolymer B can be determined according to methods well known to those skilled in the art, or can be theoretically calculated based on the molar ratio of their raw materials.

[0123] Example 1

[0124] A self-healing, self-cleaning, weather-resistant coating for the bottom surface of iron pads is composed of component A and component B mixed in a ratio of isocyanate index 1.05. The raw materials of component A and component B by mass are shown in Table 1 below.

[0125] Table 1

[0126]

[0127] Isocyanate prepolymer A is prepared from 89.2 parts of isophorone diisocyanate, 10.7 parts of trimethylolpropane, and 0.1 parts of catalyst H05. The preparation method of isocyanate prepolymer A includes the following steps: mixing isophorone diisocyanate, trimethylolpropane, and catalyst H05, and maintaining the temperature at 40°C for 3 hours to obtain isocyanate prepolymer A, wherein the isocyanate content of isocyanate prepolymer A is 27%.

[0128] Isocyanate prepolymer B is prepared from 30.8 parts of isophorone diisocyanate, 69.1 parts of polytetrahydrofuran ether diol 1000, and 0.1 parts of catalyst H05. The preparation method of isocyanate prepolymer B includes the following steps: mixing isophorone diisocyanate, polytetrahydrofuran ether diol 1000, and catalyst H05, maintaining the temperature at 90°C for 3 hours, and then stopping heating to obtain isocyanate prepolymer B; the isocyanate content of isocyanate prepolymer B is 5.83%.

[0129] In this embodiment, the amino equivalent of polyaspartic acid esters PAE-1-2 is 1340.4±2 g / eq, the amino equivalent of PAE-2-2 is 399.5±2 g / eq, and the amino equivalent of PAE-3-2 is 525.7±2 g / eq. The amino equivalent of the polyaspartic acid esters can be determined using methods well-known to those skilled in the art, or it can be theoretically calculated based on the molar ratio of the raw materials. The hydroxyl equivalent of RUVA-1 prepared in this embodiment is 397.5 g / eq - 402 g / eq.

[0130] The preparation method of the above-mentioned self-healing, self-cleaning, weather-resistant coating for the bottom surface of iron pads includes the following steps:

[0131] S1. Preparation of Component A

[0132] Polyaspartic acid ester PAE-1, polyaspartic acid ester PAE-2, polyaspartic acid ester PAE-3, mica powder, wetting and dispersing agent, defoamer, reactive ultraviolet absorber, zinc phosphate, and barium sulfate were mixed and dispersed at a stirring speed of 700 rpm for 30 min. Then, the mixture was ground to a fineness ≤15 μm. Leveling agent, black paste, and anti-settling agent were added, and the mixture was stirred at a stirring speed of 800 rpm for 20 min. The mixture was then sealed and stored to obtain component A.

[0133] Preparation of S2.B component

[0134] Isocyanate prepolymer A, isocyanate prepolymer B, hexamethylene diisocyanate trimer, and butyl acetate were mixed and stirred at a speed of 60 r / min for 45 min to obtain component B.

[0135] S3. Mix components A and B at a stirring speed of 300 r / min for 25 min.

[0136] Example 2

[0137] A self-healing, self-cleaning, weather-resistant coating for the bottom surface of iron pads is composed of component A and component B mixed in a ratio of isocyanate index 1.1. The raw materials of component A and component B by mass are shown in Table 2 below.

[0138] Table 2

[0139]

[0140] Isocyanate prepolymer A is prepared from 87 parts of isophorone diisocyanate, 11 parts of trimethylolpropane and 0.05 parts of catalyst H09; the preparation method of isocyanate prepolymer A includes the following steps: mixing isophorone diisocyanate, trimethylolpropane and catalyst H09, and keeping at 45°C for 2.5 h to obtain isocyanate prepolymer A;

[0141] Isocyanate prepolymer B is prepared from 33 parts of isophorone diisocyanate, 66.8 parts of polytetrahydrofuran ether diol 1000 and 0.15 parts of catalyst PC-02; the preparation method of isocyanate prepolymer B includes the following steps: mixing isophorone diisocyanate, polytetrahydrofuran ether diol 1000 and catalyst PC-02, keeping at 85°C for 3.5 h, stopping heating, and obtaining isocyanate prepolymer B;

[0142] The preparation method of the above-mentioned self-healing, self-cleaning, weather-resistant coating for the bottom surface of iron pads includes the following steps:

[0143] S1. Preparation of Component A

[0144] Polyaspartic acid ester PAE-1, polyaspartic acid ester PAE-2, polyaspartic acid ester PAE-3, mica powder, wetting and dispersing agent, defoamer, reactive ultraviolet absorber, zinc phosphate, and barium sulfate were mixed and dispersed at a stirring speed of 800 rpm for 20 min. Then, the mixture was ground to a fineness ≤15 μm. Leveling agent, black paste, and anti-settling agent were added, and the mixture was stirred at a stirring speed of 900 rpm for 15 min. The mixture was then sealed and stored to obtain component A.

[0145] Preparation of S2.B component

[0146] Isocyanate prepolymer A, isocyanate prepolymer B, hexamethylene diisocyanate trimer, and butyl acetate were mixed and stirred at a speed of 80 r / min for 30 min to obtain component B.

[0147] S3. Mix components A and B at a stirring speed of 350 r / min for 20 min.

[0148] Example 3

[0149] A self-healing, self-cleaning, weather-resistant coating for the bottom surface of iron pads is composed of component A and component B mixed in a ratio of isocyanate index of 1.05. The raw materials of component A and component B by mass are shown in Table 3 below.

[0150] Table 3

[0151]

[0152] Isocyanate prepolymer A is prepared from 89.2 parts of isophorone diisocyanate, 10.7 parts of trimethylolpropane, and 0.1 parts of catalyst H05. The preparation method of isocyanate prepolymer A includes the following steps: mixing isophorone diisocyanate, trimethylolpropane, and catalyst H05, and maintaining the temperature at 40°C for 3 hours to obtain isocyanate prepolymer A, wherein the isocyanate content of isocyanate prepolymer A is 27%.

[0153] Isocyanate prepolymer B is prepared from 30.8 parts of isophorone diisocyanate, 69.1 parts of polytetrahydrofuran ether diol 1000, and 0.1 parts of catalyst H05. The preparation method of isocyanate prepolymer B includes the following steps: mixing isophorone diisocyanate, polytetrahydrofuran ether diol 1000, and catalyst H05, maintaining the temperature at 90°C for 3 hours, and then stopping heating to obtain isocyanate prepolymer B; the isocyanate content of isocyanate prepolymer B is 5.83%.

[0154] The preparation method of the above-mentioned self-healing, self-cleaning, weather-resistant coating for the bottom surface of iron pads includes the following steps:

[0155] S1. Preparation of Component A

[0156] Polyaspartic acid ester PAE-1, polyaspartic acid ester PAE-2, polyaspartic acid ester PAE-3, mica powder, wetting and dispersing agent, defoamer, reactive ultraviolet absorber, zinc phosphate, and barium sulfate were mixed and dispersed at a stirring speed of 750 rpm for 25 min. Then, the mixture was ground to a fineness of ≤15 μm. Leveling agent, black paste, and anti-settling agent were added, and the mixture was stirred at a stirring speed of 850 rpm for 18 min. The mixture was then sealed and stored to obtain component A.

[0157] Preparation of S2.B component

[0158] Isocyanate prepolymer A, isocyanate prepolymer B, hexamethylene diisocyanate trimer, and butyl acetate were mixed and stirred at a speed of 70 r / min for 40 min to obtain component B.

[0159] S3. Mix components A and B at a stirring speed of 300 r / min for 20 min.

[0160] Example 4

[0161] A self-healing, self-cleaning, weather-resistant coating for the bottom surface of iron pads is composed of component A and component B mixed in a ratio of isocyanate index 1. The raw materials of component A and component B by mass are shown in Table 4 below.

[0162] Table 4

[0163]

[0164] Isocyanate prepolymer A is prepared from 92 parts of isophorone diisocyanate, 9 parts of trimethylolpropane and 0.15 parts of catalyst PC-02; the preparation method of isocyanate prepolymer A includes the following steps: mixing isophorone diisocyanate, trimethylolpropane and catalyst PC-02, and holding at 35°C for 3.5 h to obtain isocyanate prepolymer A;

[0165] Isocyanate prepolymer B is prepared from 29 parts of isophorone diisocyanate, 70.5 parts of polytetrahydrofuran ether diol 1000 and 0.05 parts of catalyst H09; the preparation method of isocyanate prepolymer B includes the following steps: mixing isophorone diisocyanate, polytetrahydrofuran ether diol 1000 and catalyst H09, keeping at 95°C for 2.5 h, stopping heating, and obtaining isocyanate prepolymer B;

[0166] The preparation method of the above-mentioned self-healing, self-cleaning, weather-resistant iron pad bottom surface integrated coating is the same as in Example 1.

[0167] Example 5

[0168] A self-healing, self-cleaning, weather-resistant coating for the bottom surface of iron pads is composed of component A and component B mixed in a ratio of isocyanate index of 1.05. The raw materials of component A and component B by mass are shown in Table 5.

[0169] Table 5

[0170]

[0171] Isocyanate prepolymer A is prepared from 89.2 parts of isophorone diisocyanate, 10.7 parts of trimethylolpropane and 0.1 parts of catalyst H05; the preparation method of isocyanate prepolymer A includes the following steps: mixing isophorone diisocyanate, trimethylolpropane and catalyst H05, and keeping at 40°C for 3 hours to obtain isocyanate prepolymer A;

[0172] Isocyanate prepolymer B is prepared from 30.8 parts of isophorone diisocyanate, 69.1 parts of polytetrahydrofuran ether diol 1000 and 0.1 parts of catalyst H05; the preparation method of isocyanate prepolymer B includes the following steps: mixing isophorone diisocyanate, polytetrahydrofuran ether diol 1000 and catalyst H05, keeping at 90°C for 3 hours, stopping heating, and obtaining isocyanate prepolymer B;

[0173] The preparation method of the above-mentioned self-healing, self-cleaning, weather-resistant iron pad bottom surface integrated coating is the same as in Example 1.

[0174] Example 6

[0175] A self-healing, self-cleaning, weather-resistant coating for the bottom surface of iron pads is composed of component A and component B mixed in a ratio of isocyanate index of 1.05. The raw materials of component A and component B by mass are shown in Table 6 below.

[0176] Table 6

[0177]

[0178] Isocyanate prepolymer A is prepared from 89.2 parts of isophorone diisocyanate, 10.7 parts of trimethylolpropane and 0.1 parts of catalyst H05; the preparation method of isocyanate prepolymer A includes the following steps: mixing isophorone diisocyanate, trimethylolpropane and catalyst H05, and keeping at 40°C for 3 hours to obtain isocyanate prepolymer A;

[0179] Isocyanate prepolymer B is prepared from 30.8 parts of isophorone diisocyanate, 69.1 parts of polytetrahydrofuran ether diol 1000 and 0.1 parts of catalyst H05; the preparation method of isocyanate prepolymer B includes the following steps: mixing isophorone diisocyanate, polytetrahydrofuran ether diol 1000 and catalyst H05, keeping at 90°C for 3 hours, stopping heating, and obtaining isocyanate prepolymer B;

[0180] The preparation method of the above-mentioned self-healing, self-cleaning, weather-resistant iron pad bottom surface integrated coating is the same as in Example 1.

[0181] Example 7

[0182] A self-healing, self-cleaning, weather-resistant coating for the bottom surface of an iron pad is provided. Compared with Example 3, the only difference is that the reactive ultraviolet absorber is replaced with ultraviolet absorber UV327; the preparation method of the coating is the same as that of Example 3.

[0183] Comparative Example 1

[0184] Compared with Example 3, the only difference is that isocyanate prepolymer A is replaced with isocyanate prepolymer B with the same isocyanate content.

[0185] Comparative Example 2

[0186] Compared with Example 3, the only difference is that isocyanate prepolymer B is replaced with isocyanate prepolymer A with the same isocyanate content.

[0187] Comparative Example 3

[0188] Compared with Example 3, the only difference is that polyaspartic acid ester PAE-1-2 is replaced with polyaspartic acid ester PAE-2-2 with the same amino content.

[0189] Comparative Example 4

[0190] Compared with Example 3, the only difference is that polyaspartic acid ester PAE-2-2 is replaced with polyaspartic acid ester PAE-1-2 with the same amino content.

[0191] Comparative Example 5

[0192] Compared with Example 3, the only difference is that polyaspartic acid ester PAE-3-2 is replaced with polyaspartic acid ester PAE-2-2 with an equal amino equivalent.

[0193] Test case

[0194] The coatings prepared in the examples and comparative examples were subjected to performance tests, and the results are shown in Table 7 below.

[0195] The detection methods are as follows:

[0196] Adhesion (pull-off test): Refer to GB / T5210-2006, expressed as the maximum tensile force required to pull off a unit area of ​​the paint film.

[0197] Salt spray resistance: Refer to GB / T1771-2007, requirements: no rust, no cracking, no peeling. Record the time until rust, cracking, or peeling defects appear on the paint film.

[0198] Weather resistance was determined by the following method: The test was conducted according to GB / T 1865-2009, and the coated samples were artificially accelerated aged in a xenon lamp aging test chamber; the samples were periodically removed, and the chalking, gloss loss and discoloration grades of the paint film were evaluated according to GB / T 1766-2008. The cumulative aging time when any of the above three indicators first exceeded grade 2 was taken as the weather resistance characterization value of the coating.

[0199] Bending performance, i.e. flexibility: Refer to GB / T1731-2020, expressed as the minimum shaft diameter that does not cause damage to the paint film.

[0200] Impact resistance: Refer to GB / T1732-2020, expressed as the maximum impact height that will not cause damage to the paint film.

[0201] Salt water resistance: Refer to GB / T 9274-1988. Requirements: no blistering, no peeling, no cracking. Record the time until the paint film shows defects such as rusting, cracking, and peeling.

[0202] All the above tests were conducted under the specified substrate and film thickness of 80 µm ± 5 µm dry film.

[0203] Table 7

[0204]

[0205] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A self-healing, self-cleaning, weather-resistant coating for the bottom surface of iron pads, characterized in that, It is composed of component A and component B mixed in a ratio of isocyanate index of 1 to 1.1; wherein, by mass parts, component A includes: 26 to 31 parts polyaspartic acid ester PAE-1, 26 to 29 parts polyaspartic acid ester PAE-2, 4 to 8 parts polyaspartic acid ester PAE-3, 3 to 5 parts mica powder, 1 to 3 parts wetting and dispersing agent, 0.5 to 1 part defoamer, 0.3 to 0.6 parts leveling agent, 0 to 3 parts color paste, 2 to 4 parts anti-settling agent, 5 to 8 parts ultraviolet absorber, and 13.2 to 2 parts [unclear text - possibly a chemical formula or ingredient]. 4.9 parts zinc phosphate, 1-4 parts barium sulfate; Component B includes 7-12 parts isocyanate prepolymer A, 16-22 parts isocyanate prepolymer B, 65-75 parts hexamethylene diisocyanate trimer, 2-4 parts butyl acetate; the polyaspartic acid ester PAE-1 is a polyaspartic acid ester containing polydimethylsiloxane segments; the polyaspartic acid ester PAE-2 is a polyaspartic acid ester containing disulfide bonds; the polyaspartic acid ester PAE-3 is a polyaspartic acid ester containing disulfide bonds and silane coupling groups; The isocyanate prepolymer A is polymerized from isophorone diisocyanate and trimethylolpropane under the action of a catalyst; the isocyanate prepolymer B is polymerized from isophorone diisocyanate and polytetrahydrofuran ether diol under the action of a catalyst. The polyaspartic acid ester PAE-2 is obtained by esterification of maleic anhydride with 2,2'-dithiodiethanol and n-octanol, followed by Michael addition reaction of the esterification product with cyclohexylmethylamine.

2. The self-healing, self-cleaning, weather-resistant coating for the bottom surface of an iron pad as described in claim 1, characterized in that, The polyaspartic acid ester PAE-1 is obtained by esterification of maleic anhydride and n-octanol, followed by Michael addition reaction of the esterification product with diaminopropyl polydimethylsiloxane.

3. The self-healing, self-cleaning, weather-resistant coating for the bottom surface of an iron pad as described in claim 1, characterized in that, The polyaspartic acid ester PAE-3 is obtained by esterification of maleic anhydride with 2,2'-dithiodiethanol and n-octanol, followed by Michael addition reaction of the esterification product with γ-aminopropyltriethoxysilane.

4. The self-healing, self-cleaning, weather-resistant coating for the bottom surface of an iron pad as described in claim 1, characterized in that, The raw materials of the polyaspartic acid ester PAE-1 include the following components in parts by weight: 6.5 to 7.8 parts maleic anhydride, 17.5 to 21.5 parts n-octanol and 70.5 to 75.7 parts diaminopropyl polydimethylsiloxane.

5. The self-healing, self-cleaning, weather-resistant coating for the bottom surface of an iron pad as described in claim 1, characterized in that, The raw materials of the polyaspartic acid ester PAE-2 include the following components in parts by weight: 22.5-24.6 parts maleic anhydride, 17.6-18.9 parts 2,2'-dithiodiethanol, 30.3-33.1 parts n-octanol and 25.7-28.3 parts cyclohexylmethylamine.

6. The self-healing, self-cleaning, weather-resistant coating for the bottom surface of an iron pad as described in claim 1, characterized in that, The raw materials of the polyaspartic acid ester PAE-3 include the following components in parts by weight: 17.4-19.8 parts maleic anhydride, 13.7-15.1 parts 2,2'-dithiodiethanol, 22.9-25.7 parts n-octanol and 40.9-43.6 parts γ-aminopropyltriethoxysilane.

7. The self-healing, self-cleaning, weather-resistant coating for the bottom surface of an iron pad as described in claim 1, characterized in that, The ultraviolet absorber is a reactive ultraviolet absorber, which is obtained by ring-opening esterification of 3-[3-(2-H-benzotriazol-2-yl)-4-hydroxy-5-tert-butylphenyl]-propionic acid and octyl glycidyl ether in the presence of a catalyst.

8. The method for preparing the self-healing, self-cleaning, weather-resistant coating for the bottom surface of an iron pad as described in any one of claims 1 to 7, characterized in that, Includes the following steps: S1. Preparation of Component A Polyaspartic acid ester PAE-1, polyaspartic acid ester PAE-2, polyaspartic acid ester PAE-3, mica powder, wetting and dispersing agent, defoamer, reactive ultraviolet absorber, zinc phosphate and barium sulfate are mixed and dispersed, then ground to a fineness ≤15um, and then leveling agent, color paste and anti-settling agent are added, stirred and mixed, and stored in a sealed container to obtain component A; Preparation of S2.B component Isocyanate prepolymer A, isocyanate prepolymer B, hexamethylene diisocyanate trimer and butyl acetate were mixed and stirred to obtain component B; S3. Mix components A and B.

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