Single-component self-healing polyurethane heavy anti-corrosion coating and preparation method thereof

Abstract

The invention provides a single-component self-healing polyurethane heavy anti-corrosion coating and a preparation method thereof. The single-component self-healing polyurethane heavy anti-corrosion coating comprises polyurethane containing DA reversible covalent bonds and an organic solvent, the polyurethane containing the DA reversible covalent bond is prepared from polymer polyol, isophorone isocyanate, a first organic tin catalyst, a diol chain extender, N-(2-ethoxyl) maleimide and double-end furyl polyurethane small molecules; the double-end furyl polyurethane micromolecule is prepared from furfuryl alcohol, tetrahydrofuran, dicyclohexylmethane-4, 4 '-diisocyanate and a second organic tin catalyst. The heavy anti-corrosion coating disclosed by the invention has excellent anti-yellowing characteristic, hydrolysis resistance and chemical resistance, so that the heavy anti-corrosion coating has long-acting anti-corrosion performance. In addition, after the coating is damaged, cracks can be rapidly repaired through heating, and the corrosion resistance of the repaired coating can be remarkably improved.

Description

Technical Field

[0001] The invention belongs to the technical field of heavy-duty anti-corrosion coatings, and in particular relates to a single-component self-healing polyurethane heavy-duty anti-corrosion coating and a preparation method thereof. Background Art

[0002] Marine corrosion can lead to damage and failure of marine engineering steel structures, and also have a serious impact on the marine ecological environment. Applying organic coating on the surface is one of the effective means to improve the corrosion resistance of marine engineering steel structures, and it is also an indispensable and important link. However, due to environmental aging, external force damage and other effects, organic coatings will inevitably produce defects such as damage and cracking, providing diffusion channels for corrosive media, resulting in the failure of the coating's anti-corrosion performance.

[0003] Coatings with self-healing ability can automatically or under certain conditions repair damage after damage and restore physical barrier properties, and are gaining more and more attention. According to the different ways of supplying materials and energy, self-healing systems can be divided into external-aided and intrinsic types. External-aided self-healing coatings are introduced into the material. When the material is damaged and cracks occur, the internal explants are released and move to the microcracks to repair the cracks. However, the explant content in the coating is limited or the fluidity is poor, making it difficult to respond quickly to coating damage and unable to repair macro cracks multiple times. Intrinsic self-healing coatings do not require the introduction of repair agents from the outside, but through the intermolecular forces, the material is repaired once or even multiple times. However, the anti-corrosion performance of the repaired coating will be reduced, and it is difficult to use it for a long time in the heavy anti-corrosion environment of the ocean. Therefore, it is very necessary to develop a self-healing coating material that can be applied to the heavy anti-corrosion of marine engineering steel structures, which can not only realize multiple repairs of cracks without the introduction of external repair agents, but also ensure that the anti-corrosion performance of the repaired coating is better, thereby realizing the long-term anti-corrosion of the coating in the harsh marine environment. Summary of the invention

[0004] In view of this, the present invention aims to overcome the defects in the prior art and proposes a one-component self-healing polyurethane heavy anti-corrosion coating and a preparation method thereof. The heavy anti-corrosion coating prepared by the present invention belongs to a one-component system, which is obtained by self-curing a polyurethane polymer containing a DA reversible covalent bond at a certain temperature. The polyurethane polymer is synthesized from the raw materials of isophorone diisocyanate and dicyclohexylmethane-4,4'-diisocyanate, which can ensure that the coating has excellent anti-yellowing properties, hydrolysis resistance and chemical resistance, thereby having long-term anti-corrosion performance. In addition, after the coating is damaged, not only can the cracks be quickly repaired by heating, but the anti-corrosion performance of the repaired coating will be significantly improved.

[0005] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0006] In a first aspect, the present invention provides a one-component self-healing polyurethane heavy anti-corrosion coating, comprising a polyurethane containing a DA reversible covalent bond and an organic solvent in a mass ratio of (1-100): (0.4-10);

[0007] The polyurethane containing DA reversible covalent bonds is prepared from the following components:

[0008] Polymer polyol, isophorone isocyanate, a first organotin catalyst, a diol chain extender, N-(2-hydroxyethyl) maleimide, and a double-terminal furan-based polyurethane small molecule, wherein the mass ratio of the polymer polyol, isophorone isocyanate, the first organotin catalyst, the diol chain extender, N-(2-hydroxyethyl) maleimide, and the double-terminal furan-based polyurethane small molecule is (2-4): (1.5-3): (0.1-0.15): (0.4-1): (0.5-2): (0.5-2);

[0009] The double-terminal furan-based polyurethane small molecule is prepared from the following components: furfuryl alcohol, dicyclohexylmethane-4,4'-diisocyanate, a second organotin catalyst, and tetrahydrofuran, wherein the mass / volume ratio of furfuryl alcohol, dicyclohexylmethane-4,4'-diisocyanate, the second organotin catalyst, and tetrahydrofuran is (6-12) g: (8-16) g: (0.3-1) g: (10-40) mL. In some embodiments of the present invention, the polymer polyol is one or a mixture of two or more of polypropylene glycol, polyethylene glycol, and polycarbonate diol.

[0010] In some embodiments of the present invention, the diol chain extender is one or a mixture of two or more of 1,4-butanediol, ethylene glycol, and resorcinol bis(2-hydroxyethyl) ether.

[0011] In some embodiments of the present invention, the method for preparing the double-terminated furanyl polyurethane comprises the following steps:

[0012] Furfuryl alcohol, tetrahydrofuran and a second organotin catalyst are mixed, and dicyclohexylmethane-4,4'-diisocyanate is added under nitrogen protection to obtain a mixed solution. The mixed solution is reacted at room temperature for 0.5-1h, and then the temperature is increased to 55-65°C and stirring is continued for 3-6h. After the reaction is completed, tetrahydrofuran is removed by reduced pressure distillation to obtain a double-terminal furan-based polyurethane small molecule.

[0013] In some embodiments of the present invention, the method for preparing the polyurethane containing DA reversible covalent bonds comprises the following steps:

[0014] The polymer polyol and isophorone isocyanate are mixed, heated to 80-90°C, and then the first organic tin catalyst is added to react to obtain a linear isocyanate group-terminated oligomer. The temperature is reduced to 70-80°C, and a diol chain extender is added. After the reaction is continued for 2-4 hours, N-(2-hydroxyethyl) maleimide is added and the reaction is continued at 70-80°C for 2-4 hours. The temperature is reduced to 55-65°C, and a double-terminal furan-based polyurethane small molecule is added. The reaction is continued for 0.5-3 hours to obtain a polyurethane containing a DA reversible covalent bond.

[0015] In some embodiments of the present invention, the mass ratio of the polyurethane containing DA reversible covalent bonds to the organic solvent is 5:2.

[0016] In some embodiments of the present invention, the first organotin catalyst and the second organotin catalyst are independently selected from any one of dibutyltin dilaurate and stannous octoate.

[0017] In some embodiments of the present invention, the organic solvent is one or a mixture of two or more of a ketone solvent, an ester solvent, and an aromatic hydrocarbon solvent. The polyurethane synthesized in the present invention contains DA reversible covalent bonds and isocyanate bonds, is soluble in organic solvents such as ketones, esters, and aromatic hydrocarbons, and can be self-cured under heating conditions without the need for an external curing agent.

[0018] In some embodiments of the present invention, the organic solvent is one or a mixture of two or more of acetone, methyl ethyl ketone, cyclohexanone, N,N-dimethylformamide, N,N-dimethylacetamide, acetamide, ethyl acetate, butyl acetate, ethylene glycol ethyl ether acetate, and toluene.

[0019] In a second aspect, the present invention also provides a method for preparing the above-mentioned single-component self-healing polyurethane heavy anti-corrosion coating, comprising the following steps:

[0020] S1: Furfuryl alcohol, tetrahydrofuran and a second organotin catalyst are mixed, and dicyclohexylmethane-4,4'-diisocyanate is added under nitrogen protection to obtain a mixed solution, the mixed solution is reacted at room temperature for 0.5-1h, and then the temperature is increased to 55-65°C and stirred for 3-6h. After the reaction is completed, tetrahydrofuran is removed by vacuum distillation to obtain a double-terminal furan-based polyurethane small molecule;

[0021] S2: Mix the polymer polyol and isophorone isocyanate, heat to 80-90°C, add the first organotin catalyst, react to obtain a linear isocyanate group-terminated oligomer, reduce the temperature to 70-80°C, add a diol chain extender, continue to react for 2-4 hours, add N-(2-hydroxyethyl)maleimide, continue to react at 70-80°C for 2-4 hours, reduce the temperature to 55-65°C, add the double-terminal furan-based polyurethane small molecule prepared in step S1, continue to react for 0.5-3 hours, and obtain a polyurethane containing a DA reversible covalent bond;

[0022] S3: The polyurethane containing DA reversible covalent bonds obtained in step S2 is evenly mixed with an organic solvent, coated on a metal substrate, cured at room temperature for 12-36 hours, dried at 50-70°C for 8-48 hours, and dried at 70-90°C for 8-48 hours to obtain a self-repairing polyurethane heavy anti-corrosion coating.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] (1) The polyurethane polymer used to prepare the one-component self-healing polyurethane heavy anti-corrosion coating in the present invention contains a DA reversible covalent bond and belongs to a one-component self-curing system. After the coating is damaged, cracks can be quickly repaired by heating;

[0025] (2) The polyurethane used to prepare the one-component self-healing polyurethane heavy anti-corrosion coating in the present invention is synthesized from raw materials of isophorone diisocyanate and dicyclohexylmethane-4,4'-diisocyanate, so that the coating has excellent anti-yellowing properties, hydrolysis resistance and chemical resistance, thereby ensuring the long-term anti-corrosion performance of the coating;

[0026] (3) The present invention uses isophorone diisocyanate (IPDI) to react with high molecular weight polypropylene glycol, and uses a diol chain extender to extend the chain to synthesize a polyurethane polymer. The anti-corrosion coating prepared from such high molecular weight polyurethane has a dense internal structure, extremely strong anti-seepage and impermeable properties, and can effectively prevent water molecules from invading;

[0027] (4) The long molecular chain of the polyurethane polymer containing DA reversible covalent bonds synthesized by the present invention is combined with a rigid segment and a flexible segment, so that after the coating is damaged, the migration and arrangement of the molecular chains during the heating repair process will eliminate the internal defects of the coating, thereby significantly improving the anti-corrosion performance of the repaired coating, and having great application potential in the field of heavy corrosion protection in marine environments;

[0028] (5) The polymer synthesis and coating preparation methods of the present invention are reasonable, the raw materials are easily available, the operation is simple, and it is conducive to promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The reaction route for preparing a single-component self-healing polyurethane heavy anti-corrosion coating according to Example 1;

[0030] Figure 2 This is the infrared spectrum of the DA reversible covalent bond polyurethane prepared in Example 1;

[0031] Figure 3 A comparison chart of low-frequency electrochemical impedance values ​​of the anti-corrosion coatings prepared in Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 3;

[0032] Figure 4 The EIS spectra of the anti-corrosion coatings prepared in Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 3 before and after repair;

[0033] Figure 5 These are optical microscope pictures of the anti-corrosion coatings prepared in Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 3 before and after repair. DETAILED DESCRIPTION

[0034] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be understood as limiting the present invention.

[0035] Unless defined otherwise herein, 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 application belongs.

[0036] Where values ​​are described herein as a range, it should be understood that such disclosure includes disclosure of all possible sub-ranges within that range, as well as specific values ​​falling within that range, regardless of whether a specific value or a specific sub-range is explicitly stated.

[0037] In this document, "multiple" and the like, unless otherwise specified, refer to a number greater than 2 or equal to 2. For example, "one or more" means one or greater than or equal to two.

[0038] In this document, the terms “preferred” and “more preferred” are only used to describe implementation methods or examples with better effects, and it should be understood that they do not constitute limitations on the scope of protection of the present invention.

[0039] In this document, the words "further" and the like are used for descriptive purposes to indicate differences in content, but should not be construed as limiting the scope of protection of the present invention.

[0040] In this article, the term "and / or" is a description of the association relationship of objects, indicating that three relationships may exist. For example, A and / or B means: A or B, or A and B.

[0041] As used herein, the term "about" means + / - 10%, preferably + / - 5%, more preferably + / - 1% of the specified value.

[0042] The terms “include,” “including,” “have,” “contain,” etc. used in this article are open-ended terms, meaning including but not limited to.

[0043] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the invention pertains. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention.

[0044] The present invention will be described in detail below with reference to the embodiments.

[0045] Example 1

[0046] A method for preparing a one-component self-healing polyurethane heavy anti-corrosion coating, the reaction route is as follows Figure 1 As shown. It includes the following steps:

[0047] S1: Preparation of small molecules containing double-terminal furan groups (HFA)

[0048] 9.80g furfuryl alcohol, 20ml tetrahydrofuran and 0.50g dibutyltin dilaurate (DBTDL) were added to a dry three-necked flask, and 13.12g dicyclohexylmethane-4,4'-diisocyanate (HMDI) was added dropwise to the three-necked flask under vigorous stirring. The reaction was stirred at room temperature for 40min, and then the temperature was raised to 60℃ and stirred for 4h. After the reaction was completed, tetrahydrofuran was removed by vacuum distillation to obtain a double-terminal furan group molecule, which was recorded as HFA.

[0049] S2: Preparation of polyurethane containing Diels-Alder (DA) reversible covalent bonds

[0050] First, 3.1g of polypropylene glycol (PPG2000) was added to the reaction round-bottom flask and dehydrated at 80°C for 8h in a vacuum drying oven. 2.53g of isophorone isocyanate (IPDI) was added to the round-bottom flask, and the round-bottom flask was placed in an oil bath and heated to 85°C. Then, 0.1g of DBTDL was added and slowly stirred for 2h to obtain a linear isocyanate group-terminated oligomer. Then, the temperature was lowered to 75°C, and 0.57g of 1,4-butanediol (BDO) dissolved in 1.25mL of N-methylpyrrolidone (NMP) was slowly added dropwise to the above mixture, and the reaction was continued for 3h. 1.00g of N-(2-hydroxyethyl) maleimide (HEMI) dissolved in 1ml of NMP was added dropwise to the reaction, and the reaction was continued at 75°C for 3h. Then, the temperature of the system was lowered to 60° C., 1.00 g of HFA dissolved in 3 ml of NMP was added, and the reaction was continued for 1 hour. After the reaction was completed, the obtained polyurethane containing DA reversible covalent bonds was cooled to room temperature for storage.

[0051] The infrared spectrum of the prepared polyurethane containing DA reversible covalent bonds is as follows: Figure 2 shown.

[0052] S3: Preparation of self-repairing polyurethane heavy-duty anti-corrosion coating

[0053] The polyurethane containing DA reversible covalent bonds prepared in step S3 and acetone were weighed in a mass ratio of 5:2, and a uniform solution was obtained by magnetic stirring. The solution was brushed onto the treated metal substrate by a brush coating method, and then cured at room temperature for 24 hours, dried at 60°C for 8 hours, and dried at 80°C for 8 hours to obtain a single-component self-healing polyurethane heavy anti-corrosion coating.

[0054] Example 2

[0055] S1: Preparation of small molecules containing double-terminal furan groups (HFA)

[0056] 6g of furfuryl alcohol, 10ml of tetrahydrofuran and 0.30g of dibutyltin dilaurate (DBTDL) were added to a dry three-necked flask, and 8g of dicyclohexylmethane-4,4'-diisocyanate (HMDI) was added dropwise to the three-necked flask under vigorous stirring. The reaction was stirred at room temperature for 30 minutes, and then the temperature was raised to 55°C and stirred for 6 hours. After the reaction was completed, tetrahydrofuran was removed by vacuum distillation to obtain a double-terminal furan group molecule, which was recorded as HFA.

[0057] S2: Preparation of polyurethane containing Diels-Alder (DA) reversible covalent bonds

[0058] First, 3.1g of polypropylene glycol (PPG2000) was added to the reaction round-bottom flask and dehydrated at 80°C for 8h in a vacuum drying oven. 2.53g of isophorone isocyanate (IPDI) was added to the round-bottom flask, and the round-bottom flask was placed in an oil bath and heated to 80°C. Then, 0.1g of DBTDL was added and slowly stirred for 4h to obtain a linear isocyanate group-terminated oligomer. Then, the temperature was lowered to 70°C, and 0.57g of 1,4-butanediol (BDO) dissolved in 1.25mL of N-methylpyrrolidone (NMP) was slowly added dropwise to the above mixture, and the reaction was continued for 4h. 1.00g of N-(2-hydroxyethyl) maleimide (HEMI) dissolved in 1ml of NMP was added dropwise to the reaction, and the reaction was continued at 70°C for 4h. Then, the temperature of the system was lowered to 55° C., 1.00 g of HFA dissolved in 3 ml of NMP was added, and the reaction was continued for 3 hours. After the reaction was completed, the obtained polyurethane containing DA reversible covalent bonds was cooled to room temperature for storage.

[0059] S3: Preparation of self-repairing polyurethane heavy-duty anti-corrosion coating

[0060] The polyurethane containing DA reversible covalent bonds prepared in step S3 and acetone were weighed in a mass ratio of 5:2, a uniform solution was obtained by magnetic stirring, and the solution was brushed onto the treated metal substrate by a brush coating method. The solution was cured at room temperature for 36 hours, dried at 50°C for 48 hours, and dried at 70°C for 48 hours to obtain a single-component self-healing polyurethane heavy anti-corrosion coating.

[0061] Example 3

[0062] S1: Preparation of small molecules containing double-terminal furan groups (HFA)

[0063] 12g furfuryl alcohol, 40ml tetrahydrofuran and 1g dibutyltin dilaurate (DBTDL) were added to a dry three-necked flask, and 16g dicyclohexylmethane-4,4'-diisocyanate (HMDI) was added dropwise to the three-necked flask under vigorous stirring. The reaction was stirred at room temperature for 60min, and then the temperature was raised to 65℃ and stirred for 3h. After the reaction was completed, tetrahydrofuran was removed by vacuum distillation to obtain a double-terminal furan group molecule, which was recorded as HFA.

[0064] S2: Preparation of polyurethane containing Diels-Alder (DA) reversible covalent bonds

[0065] First, 3.1g of polypropylene glycol (PPG2000) was added to the reaction round-bottom flask and dehydrated at 80°C for 8h in a vacuum drying oven. 2.53g of isophorone isocyanate (IPDI) was added to the round-bottom flask, and the round-bottom flask was placed in an oil bath and heated to 90°C. Then, 0.1g of DBTDL was added and slowly stirred for 2h to obtain a linear isocyanate group-terminated oligomer. Then, the temperature was lowered to 80°C, and 0.57g of 1,4-butanediol (BDO) dissolved in 1.25mL of N-methylpyrrolidone (NMP) was slowly added dropwise to the above mixture, and the reaction was continued for 2h. 1.00g of N-(2-hydroxyethyl) maleimide (HEMI) dissolved in 1ml of NMP was added dropwise to the reaction, and the reaction was continued at 80°C for 2h. Then, the temperature of the system was lowered to 65° C., 1.00 g of HFA dissolved in 3 ml of NMP was added, and the reaction was continued for 0.5 h. After the reaction was completed, the obtained polyurethane containing DA reversible covalent bonds was cooled to room temperature for storage.

[0066] S3: Preparation of self-repairing polyurethane heavy-duty anti-corrosion coating

[0067] The polyurethane containing DA reversible covalent bonds prepared in step S3 and acetone were weighed in a mass ratio of 5:2, a uniform solution was obtained by magnetic stirring, and the solution was brushed onto the treated metal substrate by a brush coating method. The solution was cured at room temperature for 12 h, dried at 70°C for 8 h, and dried at 90°C for 8 h to obtain a single-component self-healing polyurethane heavy anti-corrosion coating.

[0068] Example 4

[0069] S1: Preparation of small molecules containing double-terminal furan groups (HFA)

[0070] 9.80g furfuryl alcohol, 20ml tetrahydrofuran and 0.50g dibutyltin dilaurate (DBTDL) were added to a dry three-necked flask, and 13.12g dicyclohexylmethane-4,4'-diisocyanate (HMDI) was added dropwise to the three-necked flask under vigorous stirring. The reaction was stirred at room temperature for 40min, and then the temperature was raised to 60℃ and stirred for 4h. After the reaction was completed, tetrahydrofuran was removed by vacuum distillation to obtain a double-terminal furan group molecule, which was recorded as HFA.

[0071] S2: Preparation of polyurethane containing Diels-Alder (DA) reversible covalent bonds

[0072] First, add 2g of polypropylene glycol (PPG2000) to the reaction round-bottom flask and remove water in a vacuum drying oven at 80°C for 8h. Add 1.5g of isophorone isocyanate (IPDI) to the round-bottom flask, place the round-bottom flask in an oil bath, heat it to 85°C, add 0.1g of DBTDL, and stir slowly for 2h to obtain a linear isocyanate group-terminated oligomer. Then, lower the temperature to 75°C, slowly drop 0.4g of 1,4-butanediol (BDO) dissolved in 1.25mL of N-methylpyrrolidone (NMP) into the above mixture, and continue to react for 3h. Add 0.5g of N-(2-hydroxyethyl)maleimide (HEMI) dissolved in 1ml of NMP to the reaction, and continue to react at 75°C for 3h. Then, the temperature of the system was lowered to 60° C., 0.5 g of HFA dissolved in 3 ml of NMP was added, and the reaction was continued for 1 hour. After the reaction was completed, the obtained polyurethane containing DA reversible covalent bonds was cooled to room temperature for storage.

[0073] S3: Preparation of self-repairing polyurethane heavy-duty anti-corrosion coating

[0074] The polyurethane containing DA reversible covalent bonds and acetone prepared in step S3 were weighed in a mass ratio of 1:10, and a uniform solution was obtained by magnetic stirring. The solution was brushed onto the treated metal substrate by a brush coating method, and then cured at room temperature for 24 hours, dried at 60°C for 8 hours, and dried at 80°C for 8 hours to obtain a single-component self-healing polyurethane heavy anti-corrosion coating.

[0075] Example 5

[0076] S1: Preparation of small molecules containing double-terminal furan groups (HFA)

[0077] 9.80g furfuryl alcohol, 20ml tetrahydrofuran and 0.50g dibutyltin dilaurate (DBTDL) were added to a dry three-necked flask, and 13.12g dicyclohexylmethane-4,4'-diisocyanate (HMDI) was added dropwise to the three-necked flask under vigorous stirring. The reaction was stirred at room temperature for 40min, and then the temperature was raised to 60℃ and stirred for 4h. After the reaction was completed, tetrahydrofuran was removed by vacuum distillation to obtain a double-terminal furan group molecule, which was recorded as HFA.

[0078] S2: Preparation of polyurethane containing Diels-Alder (DA) reversible covalent bonds

[0079] First, add 4g of polypropylene glycol (PPG2000) to the reaction round-bottom flask and remove water in a vacuum drying oven at 80°C for 8h. Add 3g of isophorone isocyanate (IPDI) to the round-bottom flask, place the round-bottom flask in an oil bath, heat it to 85°C, add 0.15g of DBTDL, and stir slowly for 2h to obtain a linear isocyanate group-terminated oligomer. Then, lower the temperature to 75°C, slowly add 1g of 1,4-butanediol (BDO) dissolved in 1.25mL of N-methylpyrrolidone (NMP) to the above mixture, and continue to react for 3h. Add 2g of N-(2-hydroxyethyl)maleimide (HEMI) dissolved in 1ml of NMP to the reaction, and continue to react at 75°C for 3h. Then, the temperature of the system was lowered to 60° C., 2 g of HFA dissolved in 3 ml of NMP was added, and the reaction was continued for 2 h. After the reaction was completed, the obtained polyurethane containing DA reversible covalent bonds was cooled to room temperature for storage.

[0080] S3: Preparation of self-repairing polyurethane heavy-duty anti-corrosion coating

[0081] The polyurethane containing DA reversible covalent bonds and acetone prepared in step S3 were weighed in a mass ratio of 100:0.4, and a uniform solution was obtained by magnetic stirring. The solution was brushed onto the treated metal substrate by a brush coating method, and then cured at room temperature for 12 h, dried at 60° C. for 24 h, and dried at 80° C. for 24 h to obtain a single-component self-healing polyurethane heavy anti-corrosion coating.

[0082] Comparative Example 1

[0083] A method for preparing a two-component polyurethane coating comprises the following steps:

[0084] S1: Preparation of polyurethane

[0085] First, 3.1g of polypropylene glycol (PPG2000) was added to a round-bottom flask for reaction, and water was removed in a vacuum drying oven at 80°C for 8h. 2.53g of isophorone isocyanate (IPDI) was added to the round-bottom flask, and the round-bottom flask was placed in an oil bath, heated to 85°C, and 3 drops of dibutyltin dilaurate (DBTDL) were added. The mixture was slowly stirred for 2h to obtain a linear isocyanate group-terminated oligomer. Then, the temperature was lowered to 75°C, and 0.57g of 1,4-butanediol (BDO) dissolved in 1.25mL of NMP was slowly added to the above mixture to extend the chain of the above intermediate product to obtain a polyurethane.

[0086] S2: Preparation of two-component polyurethane coating

[0087] Add 5.4g of polyurethane into a beaker, add 4.0g of butyl acetate and 0.3g of cyclohexanone, stir evenly, then add 1.35g of N3390 curing agent, continue to stir slowly for 30 minutes, let stand for 30 minutes, and use a brushing method to apply the above solution to the treated metal substrate. Curing at room temperature for 24 hours can obtain a two-component polyurethane coating.

[0088] Comparative Example 2

[0089] The difference between this comparative example and Example 1 is that difurfuryl disulfide is used as a double-terminated furan small molecule in the preparation of the polyurethane containing a DA reversible covalent bond, and the other steps are the same as those in Example 1. The specific steps are as follows:

[0090] S1: Preparation of polyurethane containing Diels-Alder (DA) reversible covalent bonds

[0091] First, 3.1g of polypropylene glycol (PPG2000) was added to the reaction round-bottom flask and dehydrated at 80°C for 8h in a vacuum drying oven. 2.53g of isophorone isocyanate (IPDI) was added to the round-bottom flask, and the round-bottom flask was placed in an oil bath and heated to 85°C. Then, 0.1g of DBTDL was added and slowly stirred for 2h to obtain a linear isocyanate group-terminated oligomer. Then, the temperature was lowered to 75°C, and 0.57g of 1,4-butanediol (BDO) dissolved in 1.25mL of N-methylpyrrolidone (NMP) was slowly added dropwise to the above mixture, and the reaction was continued for 3h. 1.00g of N-(2-hydroxyethyl) maleimide (HEMI) dissolved in 1ml of NMP was added dropwise to the reaction, and the reaction was continued at 75°C for 3h. Then, the temperature of the system was lowered to 60° C., 1.00 g of difurfuryl disulfide dissolved in 3 ml of NMP was added, and the reaction was continued for 1 hour. After the reaction was completed, the obtained polyurethane containing DA reversible covalent bonds was cooled to room temperature for storage.

[0092] S2: Preparation of anti-corrosion coating

[0093] The polyurethane containing DA reversible covalent bonds and acetone prepared in step S1 were weighed in a mass ratio of 5:2, and a uniform solution was obtained by magnetic stirring. The solution was brushed onto the treated metal substrate by a brush coating method, and then cured at room temperature for 24 hours, dried at 60°C for 8 hours, and dried at 80°C for 8 hours to obtain an anti-corrosion coating.

[0094] Comparative Example 3

[0095] The difference between this comparative example and Example 1 is that toluene diisocyanate is used as a raw material in the preparation of the polyurethane containing DA reversible covalent bonds, and the other steps are the same as those in Example 1. The specific steps are as follows:

[0096] S1: Preparation of small molecules containing double-terminal furan groups (HFA)

[0097] 9.80g furfuryl alcohol, 20ml tetrahydrofuran and 0.50g dibutyltin dilaurate (DBTDL) were added to a dry three-necked flask, and 13.12g dicyclohexylmethane-4,4'-diisocyanate (HMDI) was added dropwise to the three-necked flask under vigorous stirring. The reaction was stirred at room temperature for 40min, and then the temperature was raised to 60℃ and stirred for 4h. After the reaction was completed, tetrahydrofuran was removed by vacuum distillation to obtain a double-terminal furan group molecule, which was recorded as HFA.

[0098] S2: Preparation of polyurethane containing Diels-Alder (DA) reversible covalent bonds

[0099] First, add 3.1g of polypropylene glycol (PPG2000) to the reaction round-bottom flask and remove water in a vacuum drying oven at 80°C for 8h. Add 2.53g of toluene diisocyanate to the round-bottom flask, place the round-bottom flask in an oil bath, heat it to 85°C, add 0.1g of DBTDL, and stir slowly for 2h to obtain a linear isocyanate group-terminated oligomer. Then, lower the temperature to 75°C, slowly drop 0.57g of 1,4-butanediol (BDO) dissolved in 1.25mL of N-methylpyrrolidone (NMP) into the above mixture, and continue to react for 3h. 1.00g of N-(2-hydroxyethyl)maleimide (HEMI) dissolved in 1ml of NMP is added dropwise to the reaction, and the reaction is continued at 75°C for 3h. Then, the temperature of the system was lowered to 60° C., 1.00 g of HFA dissolved in 3 ml of NMP was added, and the reaction was continued for 1 hour. After the reaction was completed, the obtained polyurethane containing DA reversible covalent bonds was cooled to room temperature for storage.

[0100] S3: Preparation of anti-corrosion coating

[0101] The polyurethane containing DA reversible covalent bonds and acetone prepared in step S2 were weighed in a mass ratio of 5:2, and a uniform solution was obtained by magnetic stirring. The solution was brushed onto the treated metal substrate by a brush coating method, and then cured at room temperature for 24 hours, dried at 60°C for 8 hours, and dried at 80°C for 8 hours to obtain an anti-corrosion coating.

[0102] Effect verification:

[0103] The anti-corrosion performance and self-repairing performance of the single-component self-healing polyurethane heavy anti-corrosion coating prepared in Example 1, the two-component polyurethane coating prepared in Comparative Example 1, and the anti-corrosion coatings prepared in Comparative Example 2 and Comparative Example 3 were characterized respectively. The specific methods and results are as follows:

[0104] 1. Anti-corrosion performance test:

[0105] The anti-corrosion performance of the coating was studied using electrochemical impedance spectroscopy (EIS) using an electrochemical workstation. The EIS test frequency range was 10 -2 ~10 5 Hz, the amplitude of the sine wave signal is 20mV. The electrolytic cell adopts a three-electrode system, an iron plate coated with an organic coating (with a 3cm 2 The circular test area) was used as the working electrode, the saturated calomel electrode and platinum wire were used as the reference electrode and the counter electrode respectively. The samples were immersed in 3.5wt% NaCl solution and the EIS electrochemical performance test was carried out. In the Bode diagram, the coating low frequency 10mHz (Z f＝0.01Hz ) indicates the decrease in corrosion resistance due to the diffusion of the corrosive medium in the coating. f＝0.01Hz Above 10 8 Ω·cm 2 The coating of Z usually has very good corrosion resistance, while f＝0.01Hz Less than 10 8 Ω·cm 2 The corrosion resistance of the coating is low. Therefore, the impedance value (Z f＝0.01Hz ) can be used as a semi-quantitative indicator of coating protective performance.

[0106] Z of the anticorrosion coatings prepared in Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 3 f＝0.01Hz Value Figure 3 As shown, the Z of the coating of Example 1 f＝0.01Hz Values ​​above 10 9 Ω·cm 2 , indicating that the single-component self-healing polyurethane heavy anti-corrosion coating prepared in Example 1 has excellent corrosion resistance. Comparative Example 1 belongs to a two-component polyurethane coating, whose Z f＝0.01Hz Values ​​above 10 8 Ω·cm 2, which is lower than the Z of the coating in Example 1 f＝0.01Hz The Z values ​​of the coatings in Comparative Examples 2 and 3 are shown in Table 1. f＝0.01Hz Values ​​below 10 8 Ω·cm 2 , indicating that the corrosion resistance of both is poor.

[0107] 2. Self-healing performance test

[0108] Use a utility knife to scratch a 1 cm long "cross" scratch on the coating surface to obtain a scratched coating; place the scratched coating in an oven, adjust the temperature to 135°C, keep it warm for 30 minutes, then reduce the oven temperature to 80°C, keep it warm for 8 hours, and obtain a repaired coating. Test the electrochemical impedance of the scratched coating and the scratch repaired coating, and use an optical microscope to observe the morphology of the coating before and after repair. Figure 4 It can be seen that the electrochemical impedance of the single-component self-healing heavy-duty anti-corrosion coating after repair is higher than that before scratching. Figure 5 It can be observed that the scratches on the coating disappear, and it can be concluded that the single-component self-healing polyurethane heavy-duty anti-corrosion coating prepared in Example 1 has a strong self-repairing ability, and the anti-corrosion performance of the coating will be significantly improved after repair.

[0109] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A one-component self-healing polyurethane heavy-duty anti-corrosion coating, characterized in that: The invention comprises a polyurethane containing a DA reversible covalent bond and an organic solvent in a mass ratio of (1-100):(0.4-10); The polyurethane containing DA reversible covalent bonds is prepared from the following components: polymer polyol, isophorone isocyanate, a first organotin catalyst, a diol chain extender, N-(2-hydroxyethyl) maleimide, and a double-terminal furan-based polyurethane small molecule, wherein the mass ratio of the polymer polyol, isophorone isocyanate, the first organotin catalyst, the diol chain extender, N-(2-hydroxyethyl) maleimide, and the double-terminal furan-based polyurethane small molecule is (2-4): (1.5-3): (0.1-0.15): (0.4-1): (0.5-2): (0.5-2); The double-ended furan-based polyurethane small molecule is prepared from the following components: furfuryl alcohol, dicyclohexylmethane-4,4'-diisocyanate, a second organotin catalyst, and tetrahydrofuran, wherein the mass / volume ratio of furfuryl alcohol, dicyclohexylmethane-4,4'-diisocyanate, the second organotin catalyst, and tetrahydrofuran is (6-12) g: (8-16) g: (0.3-1) g: (10-40) mL.

2. The one-component self-healing polyurethane heavy-duty anti-corrosion coating according to claim 1, characterized in that: The polymer polyol is one or a mixture of two or more of polypropylene glycol, polyethylene glycol and polycarbonate diol.

3. The one-component self-healing polyurethane heavy-duty anti-corrosion coating according to claim 1, characterized in that: The diol chain extender is one of 1,4-butanediol, ethylene glycol, and resorcinol bis(2-hydroxyethyl) ether, or a mixture of two or more thereof.

4. The one-component self-healing polyurethane heavy-duty anti-corrosion coating according to claim 1, characterized in that: The preparation method of the double-terminal furan-based polyurethane comprises the following steps: Furfuryl alcohol, tetrahydrofuran and a second organotin catalyst are mixed, and dicyclohexylmethane-4,4'-diisocyanate is added under nitrogen protection to obtain a mixed solution. The mixed solution is reacted at room temperature for 0.5-1h, and then the temperature is increased to 55-65°C and stirring is continued for 3-6h. After the reaction is completed, tetrahydrofuran is removed by reduced pressure distillation to obtain a double-terminal furan-based polyurethane small molecule.

5. The one-component self-healing polyurethane heavy-duty anti-corrosion coating according to claim 1, characterized in that: The preparation method of the polyurethane containing DA reversible covalent bonds comprises the following steps: The polymer polyol and isophorone isocyanate are mixed, heated to 80-90°C, and then the first organic tin catalyst is added to react to obtain a linear isocyanate group-terminated oligomer. The temperature is reduced to 70-80°C, and a diol chain extender is added. After the reaction is continued for 2-4 hours, N-(2-hydroxyethyl) maleimide is added and the reaction is continued at 70-80°C for 2-4 hours. The temperature is reduced to 55-65°C, and a double-terminal furan-based polyurethane small molecule is added. The reaction is continued for 0.5-3 hours to obtain a polyurethane containing a DA reversible covalent bond.

6. The one-component self-healing polyurethane heavy-duty anti-corrosion coating according to claim 1, characterized in that: The mass ratio of the polyurethane containing DA reversible covalent bonds to the organic solvent is 5:

2.

7. The one-component self-healing polyurethane heavy-duty anti-corrosion coating according to claim 1, characterized in that: The first organotin catalyst and the second organotin catalyst are independently selected from any one of dibutyltin dilaurate and stannous octoate.

8. The one-component self-healing polyurethane heavy-duty anti-corrosion coating according to claim 1, characterized in that: The organic solvent is one or a mixture of two or more of a ketone solvent, an ester solvent, and an aromatic hydrocarbon solvent.

9. The one-component self-healing polyurethane heavy-duty anti-corrosion coating according to claim 1, characterized in that: The organic solvent is one or a mixture of two or more of acetone, methyl ethyl ketone, cyclohexanone, N,N-dimethylformamide, N,N-dimethylacetamide, acetamide, ethyl acetate, butyl acetate, ethylene glycol ethyl ether acetate, and toluene.

10. The method for preparing the one-component self-healing polyurethane heavy-duty anti-corrosion coating according to any one of claims 1 to 9, characterized in that: The steps include: S1: Furfuryl alcohol, tetrahydrofuran and a second organotin catalyst are mixed, and dicyclohexylmethane-4,4'-diisocyanate is added under nitrogen protection to obtain a mixed solution, the mixed solution is reacted at room temperature for 0.5-1h, and then the temperature is increased to 55-65°C and stirred for 3-6h. After the reaction is completed, tetrahydrofuran is removed by vacuum distillation to obtain a double-terminal furan-based polyurethane small molecule; S2: Mix the polymer polyol and isophorone isocyanate, heat to 80-90°C, add the first organotin catalyst, react to obtain a linear isocyanate group-terminated oligomer, reduce the temperature to 70-80°C, add a diol chain extender, continue to react for 2-4 hours, add N-(2-hydroxyethyl)maleimide, continue to react at 70-80°C for 2-4 hours, reduce the temperature to 55-65°C, add the double-terminal furan-based polyurethane small molecule prepared in step S1, continue to react for 0.5-3 hours, and obtain a polyurethane containing a DA reversible covalent bond; S3: The polyurethane containing DA reversible covalent bonds obtained in step S2 is evenly mixed with an organic solvent, coated on a metal substrate, cured at room temperature for 12-36 hours, dried at 50-70°C for 8-48 hours, and dried at 70-90°C for 8-48 hours to obtain a self-repairing polyurethane heavy anti-corrosion coating.

Images