Corrosion-resistant polyurea coating and preparation method thereof

Abstract

The present invention relates to the technical field of coating compositions, and in particular to a corrosion-resistant polyurea coating and a preparation method thereof. The present invention provides a modified polyurea as the main component of the polyurea coating, which relies on reversible chemical action to achieve self-repair of damaged parts. Compared with the prior art, the polyurea coating of the present invention has good mechanical properties, strong adhesion to the substrate, and exhibits good corrosion resistance in different liquid media, while the self-repairing ability can greatly improve the application range and service life of the coating.

Description

Technical Field

[0001] The invention relates to the technical field of coating compositions, and in particular to a corrosion-resistant polyurea coating and a preparation method thereof. Background Art

[0002] Polyurea is a block polymer formed by the reaction of a prepolymer (component A) and an amino-containing resin and a chain extender (component B). Its formation process mainly involves two chemical reaction mechanisms: first, when the terminal hydroxyl compound comes into contact with isocyanate, the oxygen atom of the hydroxyl group attacks the carbon atom on the isocyanate to form a carbamate bond through hydrogen transfer; second, the amino group reacts nucleophilically with the isocyanate to form a more stable urea bond with greater bond energy. In the molecular chain of polyurea, the carbamate bond and the urea bond can form a hard domain through intermolecular forces due to their large cohesive energy and volume; while the longer carbon chain can entangle with each other to form a soft domain due to its weaker polarity and stronger flexibility. Due to the large difference in polarity and free energy between the hard domain and the soft domain, microphase separation will occur between them, and the hard domain exists as an isolated rod in the soft domain. The performance of polyurea is significantly affected by the structure and content of soft and hard domains: the hard domain, as a rigidity enhancer and interchain connection, has an important influence on the molecular structure stability and mechanical properties of polyurea; the microphase-separated soft and hard domains can increase the tensile strength or elongation, especially under low temperature conditions, which can significantly improve the mechanical properties of the material and reduce the low-temperature "dehumidification" phenomenon. Since the invention of polyurea materials in the 1980s, due to its excellent anti-corrosion, waterproof, tensile and impact resistance, it has been widely used in coatings, elastomers, foams, adhesives and other fields. The excellent physical and chemical properties make polyurea have great application potential in the field of high-performance special functional coatings.

[0003] CN110423544B discloses a highly wear-resistant and anti-corrosion modified one-component polyurea coating and a preparation method thereof. The highly wear-resistant and anti-corrosion modified one-component polyurea coating comprises the following components: 35-40 parts of polytetrahydrofuran diol, 8-12 parts of dicyclohexylmethane diisocyanate, 50-54 parts of dichloromethane, 2-3 parts of liquid antioxidant, 2-3 parts of ultraviolet absorber, 2-3 parts of stabilizer, 1-2 parts of dibutyltin dilaurate, color paste, curing agent diethyltoluenediamine, the volume ratio of the curing agent component to the volume of the non-curing agent and non-color paste components is 1:31, and the weight of the color paste is 3-9 parts. The polyurea coating prepared by the present invention innovatively uses dichloromethane as a diluent, achieves a good dilution effect, and stores the curing agent component separately, so that the storage time of the polyurea coating is greatly extended.

[0004] CN117285856A discloses an anti-corrosion and wear-resistant modified polyurea coating and a processing method, the formula of which includes: polytetrahydrofuran, polyacrylic acid, polycarbonate, polyurethane elastomer, polyaspartic acid resin, epoxy resin, polyisocyanate, amine curing agent, filler, solvent, chain extender, leveling agent, anti-settling agent and defoaming agent, and the method includes step one, weighing raw materials; step two, preparing group A; step three, preparing group B; step four, mixing coating; compared with the existing polyurea coating, the invention increases the corrosion resistance and mechanical properties of the coating by adding polyurethane elastomer and polycarbonate; the invention improves the anti-microbial and anti-fungal performance of the coating by adding polytetrahydrofuran, and polytetrahydrofuran has certain hydrolysis resistance and low-temperature compliance; the invention adds better light stability to the coating by adding polyacrylic acid, thereby improving its UV resistance and extending its service life.

[0005] Although polyurea coating has excellent corrosion resistance, aging resistance and adhesion, it is inevitable that stress will cause micro cracks during service, thereby reducing the anti-corrosion performance of the coating. Therefore, how to solve this problem will be the key to improving the application scope and service life of polyurea coating. Summary of the invention

[0006] In view of the above-mentioned defects in the prior art, the technical problem to be solved by the present invention is to provide a corrosion-resistant polyurea coating and a preparation method thereof.

[0007] In the increasingly harsh and changeable use environment, such as the aerodynamic impact of high-speed aircraft, the high-salt and high-humidity environment on islands and reefs, and the harsh sea conditions during ocean voyages, anti-corrosion coatings face unprecedented challenges. Factors such as impact, wear, ultraviolet aging, and erosion by corrosive media in these environments may cause difficult-to-detect micro-damage to the coating. If these micro-damages are not treated in a timely manner, they will gradually accumulate, causing the protective performance of the coating to decline irreversibly, and may eventually lead to the failure of the entire anti-corrosion layer. Therefore, the development of a functional coating that can automatically repair these micro-damages has become an important topic. Self-healing anti-corrosion coatings came into being. It not only inherits all the basic characteristics of traditional anti-corrosion coatings, but also gives the coating the ability to self-repair micro-damages by integrating intelligent response materials or structures. This self-healing function significantly improves the durability and service life of the coating. The present invention provides a modified polyurea as the main component of a polyurea coating, which realizes self-repair of the coating by introducing a reversible dynamic covalent DA bond, and automatically repairs the damaged part by relying on a reversible chemical action. The coating does not require the addition of a repair agent, and is not limited to a specific coating damage mode, so it can achieve multiple repairs of the damage, greatly improving the repair efficiency of the coating. The polyurea is modified by obtaining an epoxy resin from 2,5-di(aminomethyl)furan and 2,2-bis-(4-glycolylaminophenyl)propane, which effectively improves the mechanical properties and adhesion, thereby making the substrate of the coating more firmly bonded, which is crucial to improving the anti-corrosion effect.

[0008] To achieve the above object, the present invention provides a method for preparing a corrosion-resistant polyurea coating, comprising the following steps:

[0009] S1. After mixing 4,4'-methylenebis(phenyl isocyanate) and polytetrahydrofuran, the mixture is heated and stirred for 1 to 2 hours under an inert atmosphere to obtain a prepolymer, and then 1H-pyrrole-2,5-dimethylamine is added. After stirring evenly, tetrahydrofuran is added to dilute the mixture, and stirring is continued for 4 to 6 hours to obtain polyurea; after mixing 2,5-di(aminomethyl)furan and 2,2-bis-(4-glycolylaminophenyl)propane, N,N-dimethylformamide is added to dilute the mixture, and the mixture is heated and stirred for 4 to 6 hours. After mixing evenly with the polyurea, 4,4'-di(maleimido)-1,1'-biphenyl is added, and the mixture is stirred at room temperature for 1 to 2 hours to obtain a modified polyurea;

[0010] S2. Evenly mix the modified polyurea with the anti-rust filler, dispersant, leveling agent and ultraviolet absorber to obtain the product.

[0011] Furthermore, the molar ratio of the 4,4'-methylenebis(phenyl isocyanate) to polytetrahydrofuran and 1H-pyrrole-2,5-dimethylamine is 1:0.4-0.6:0.5-0.6.

[0012] Furthermore, the molar ratio of the 2,5-bis(aminomethyl)furan to 2,2-bis-(4-glycolylaminophenyl)propane and 4,4'-bis(maleimido)-1,1'-biphenyl is 1:1:3-4.

[0013] Furthermore, the temperature range of the heating and stirring is 60-80°C.

[0014] Furthermore, the anti-rust filler is a mixture of one or more of mica iron oxide, zinc phosphate, aluminum phosphate, talcum powder, organic bentonite, and titanium dioxide.

[0015] Furthermore, the dispersant is BYK-163.

[0016] Furthermore, the leveling agent is EFKA-3777.

[0017] Furthermore, the ultraviolet absorber is tinuvin 1130.

[0018] Furthermore, the mass ratio of the modified polyurea to the anti-rust filler, the dispersant, the leveling agent and the ultraviolet absorber is 50-60:10-15:1-2:1-2:0.1-1.

[0019] The invention also provides a corrosion-resistant polyurea coating, which is prepared by the above method.

[0020] Beneficial effects of the present invention:

[0021] 1. Compared with the prior art, the present invention provides a modified polyurea as the main component of a polyurea coating, which realizes self-repair of the coating by introducing a reversible dynamic covalent DA bond, and automatically repairs the damaged part by relying on a reversible chemical action. This coating does not require the addition of a repair agent and is not limited to a specific coating damage mode. Therefore, it can achieve multiple repairs of the damage, greatly improving the coating repair efficiency.

[0022] 2. Compared with the prior art, the polyurea coating obtained by the present invention has good mechanical properties, strong adhesion to the substrate, and exhibits good corrosion resistance in different liquid media. DETAILED DESCRIPTION

[0023] Polytetrahydrofuran, Mw=1000.

[0024] 1H-Pyrrole-2,5-dimethanamine, CAS No.: 713501-36-1.

[0025] Example 1

[0026] A method for preparing a corrosion-resistant polyurea coating comprises the following steps, measured in parts by weight:

[0027] S1. After mixing 25 parts of 4,4'-methylenebis(phenyl isocyanate) and 50 parts of polytetrahydrofuran, the mixture was heated to 80°C and stirred for 2 hours under a nitrogen atmosphere to obtain a prepolymer, and then 7.5 parts of 1H-pyrrole-2,5-dimethylamine was added. After stirring evenly, an equal volume of tetrahydrofuran was added to dilute the mixture, and stirring was continued for 6 hours to obtain polyurea; after mixing 12.6 parts of 2,5-bis(aminomethyl)furan and 34 parts of 2,2-bis-(4-glycolylaminophenyl)propane, an equal volume of N,N-dimethylformamide was added to dilute the mixture, and the mixture was heated to 60°C and stirred for 4 hours. After mixing evenly with the polyurea, 103.2 parts of 4,4'-bis(maleimido)-1,1'-biphenyl was added, and the mixture was stirred at room temperature for 2 hours to obtain a modified polyurea;

[0028] S2. Mix 55 parts of modified polyurea, 15 parts of aluminum phosphate, 32 parts of BYK-16, 1 part of EFKA-3777 and 0.5 parts of tinuvin 1130 and obtain the product.

[0029] Example 2

[0030] A method for preparing a corrosion-resistant polyurea coating comprises the following steps, measured in parts by weight:

[0031] S1. After mixing 25 parts of 4,4'-methylenebis(phenyl isocyanate) and 40 parts of polytetrahydrofuran, the mixture was heated to 80°C and stirred for 2 hours under a nitrogen atmosphere to obtain a prepolymer, and then 7.5 parts of 1H-pyrrole-2,5-dimethylamine was added. After stirring evenly, an equal volume of tetrahydrofuran was added to dilute the mixture, and the mixture was stirred for 6 hours to obtain a polyurea; after mixing 12.6 parts of 2,5-bis(aminomethyl)furan and 34 parts of 2,2-bis-(4-glycolylaminophenyl)propane, an equal volume of N,N-dimethylformamide was added to dilute the mixture, the mixture was heated to 60°C and stirred for 4 hours, and after mixing evenly with the polyurea, 103.2 parts of 4,4'-bis(maleimido)-1,1'-biphenyl was added, and the mixture was stirred at room temperature for 2 hours to obtain a modified polyurea;

[0032] S2. Mix 55 parts of modified polyurea, 15 parts of aluminum phosphate, 32 parts of BYK-16, 1 part of EFKA-3777 and 0.5 parts of tinuvin 1130 and obtain the product.

[0033] Example 3

[0034] A method for preparing a corrosion-resistant polyurea coating comprises the following steps, measured in parts by weight:

[0035] S1. After mixing 25 parts of 4,4'-methylenebis(phenyl isocyanate) and 60 parts of polytetrahydrofuran, the mixture was heated to 80°C and stirred for 2 hours under a nitrogen atmosphere to obtain a prepolymer, and then 7.5 parts of 1H-pyrrole-2,5-dimethylamine was added. After stirring evenly, an equal volume of tetrahydrofuran was added to dilute the mixture, and the mixture was stirred for 6 hours to obtain a polyurea; after mixing 12.6 parts of 2,5-bis(aminomethyl)furan and 34 parts of 2,2-bis-(4-glycolylaminophenyl)propane, an equal volume of N,N-dimethylformamide was added to dilute the mixture, and the mixture was heated to 60°C and stirred for 4 hours. After mixing evenly with the polyurea, 103.2 parts of 4,4'-bis(maleimido)-1,1'-biphenyl was added, and the mixture was stirred at room temperature for 2 hours to obtain a modified polyurea;

[0036] S2. Mix 55 parts of modified polyurea, 15 parts of aluminum phosphate, 32 parts of BYK-16, 1 part of EFKA-3777 and 0.5 parts of tinuvin 1130 and obtain the product.

[0037] Comparative Example 1

[0038] A method for preparing a corrosion-resistant polyurea coating comprises the following steps, measured in parts by weight:

[0039] S1. Mix 25 parts of 4,4'-methylenebis(phenyl isocyanate) and 50 parts of polytetrahydrofuran, heat to 80°C and stir for 2 hours under a nitrogen atmosphere to obtain a prepolymer, then add 7.5 parts of 1H-pyrrole-2,5-dimethylamine, stir evenly, add an equal volume of tetrahydrofuran to dilute, and continue stirring for 6 hours to obtain polyurea;

[0040] S2. Mix 55 parts of polyurea, 15 parts of aluminum phosphate, 32 parts of BYK-16, 1 part of EFKA-3777 and 0.5 parts of tinuvin 1130 evenly to obtain the product.

[0041] Comparative Example 2

[0042] A method for preparing a corrosion-resistant polyurea coating comprises the following steps, measured in parts by weight:

[0043] S1. After mixing 25 parts of 4,4'-methylenebis(phenyl isocyanate) and 50 parts of polytetrahydrofuran, the mixture was heated to 80°C and stirred for 2 hours under a nitrogen atmosphere to obtain a prepolymer. After mixing 12.6 parts of 2,5-di(aminomethyl)furan and 34 parts of 2,2-bis-(4-glycolylaminophenyl)propane, an equal volume of N,N-dimethylformamide was added to dilute the mixture, the mixture was heated to 60°C and stirred for 4 hours, and the mixture was uniformly mixed with the prepolymer and stirred at room temperature for 2 hours to obtain a modified polyurea.

[0044] S2. Mix 55 parts of modified polyurea, 15 parts of aluminum phosphate, 32 parts of BYK-16, 1 part of EFKA-3777 and 0.5 parts of tinuvin 1130 evenly to obtain the product.

[0045] Test Example 1

[0046] The polyurea coatings in the embodiments and control examples were tested for mechanical properties with reference to the test method in GB / T23446-2009 "Spraying polyurea waterproof coatings", and a tensile testing machine was used to test the elongation at break and tensile strength. A dumbbell-shaped tensile test sample strip was used, and the deformation induction was calculated by point elongation (point spacing 25mm), and the tensile rate was 100mm / min. A pull-off adhesion tester was used to evaluate the adhesion of the coating. The test method is to first bond a round ingot to the surface of the coating to be tested through an adhesive, and after 24 hours of room temperature curing, the test was performed with reference to the ASTMD4541 standard. The pull-off test was repeated at least 5 times on each set of samples, and the data was recorded and averaged. The specific test results are shown in Table 1.

[0047] Table 1 Mechanical properties and adhesion test of corrosion-resistant polyurea coatings

[0048]

[0049]

[0050] As can be seen from Table 1, the mechanical properties of the embodiment are better than those of the control example, and embodiment 1 performs best among embodiments 1 to 3. This may be due to the different addition amounts of polytetrahydrofuran in different embodiments. Polytetrahydrofuran is usually used as a soft segment. Polytetrahydrofuran is easy to form crystals due to its regular structure. Therefore, when used as a soft segment in polyurethane, it can provide higher strength and flexibility. When the content of the soft segment increases, the tensile stress of the material can be improved to a certain extent. However, when the content of the soft segment is too much, excessive microphase separation may result, resulting in a decrease in mechanical properties. Compared with the embodiment, the control example does not modify the polyurea to varying degrees, and the addition of epoxy resin or other groups can improve the mechanical and other properties of the coating to a certain extent. Adding epoxy resin to the polyurea coating can introduce additional polar functional groups, such as hydroxyl and epoxy groups. These polar groups can attract each other with the polar groups on the surface of the substrate, and this attraction can enhance the adhesion of the coating to the substrate. When the polar groups in the coating attract each other with the corresponding groups on the substrate surface, they can enhance the bonding strength between the coating and the substrate by forming hydrogen bonds, electrostatic forces and van der Waals forces. This mutually attractive effect helps to improve the adhesion of the coating and reduces the possibility of peeling. Meanwhile, these polar groups can also adjust the surface tension of the coating so that it better wets the substrate surface, thereby improving the spreadability and leveling of the coating, thus not only improving the uniformity of the coating, but also enhancing its adhesion. Therefore, the coating in the embodiment shows good adhesion to the substrate.

[0051] Test Example 2

[0052] The coatings in the embodiments and control examples were subjected to corrosion resistance tests, and the alkali resistance (25% sodium hydroxide solution, 10 days), salt water resistance (immersed in boiling NaCl solution for 10 days), and acid resistance (25% hydrochloric acid, 10 days) were tested with reference to GB / T9274-1988 "Determination of resistance of paints and varnishes to liquid media". A self-repair test was performed on the coating. After scratching a 10 mm long and 5 mm deep scratch on the coating, it was placed under near-infrared light (800 nm) for irradiation and then subjected to corrosion resistance test. The specific test results are shown in Table 2.

[0053] Table 2 Corrosion resistance and self-repairing test of corrosion-resistant polyurea coating

[0054]

[0055] From the test results in Table 2, it can be seen that the coating prepared by the coating in the embodiment has better corrosion resistance. This is because the prepared coating can form a dense coating on the surface of the substrate, so that it can better isolate the contact with the liquid medium and the substrate, thereby achieving the anti-corrosion effect, and the adhesion between the coating and the substrate also greatly affects the combination of the coating and the substrate, so the corrosion resistance in the embodiment is significantly better than that in the reference example. In the reference example, since the mechanical properties and adhesion are worse than those in the embodiment, the coating is more prone to bubbling and falling off in the liquid medium, causing the substrate to rust. In reference example 1, due to the introduction of a reversible dynamic covalent bond, after repair, it can still maintain the same corrosion resistance as when there is no scratch on the surface, while in reference example 2, due to the lack of self-repairing properties, the coating has obvious corrosion after experiencing scratches. The coating in the embodiment undergoes a thermally reversible effect when it is scratched due to the heat generated by near-infrared light irradiation, thereby achieving self-repair. In the present invention, the damaged part is automatically repaired by reversible chemical action. This coating does not require the addition of a repair agent and is not limited to a specific coating damage mode. Therefore, it can achieve multiple repairs of the damage, greatly improving the repair efficiency of the coating.

[0056] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A method for preparing a corrosion-resistant polyurea coating, characterized in that: The steps include: S1. After mixing 4,4'-methylenebis(phenyl isocyanate) and polytetrahydrofuran, the mixture is heated and stirred for 1-2 hours under an inert atmosphere to obtain a prepolymer, and then 1H-pyrrole-2,5-dimethylamine is added. After stirring evenly, tetrahydrofuran is added to dilute the mixture, and stirring is continued for 4-6 hours to obtain polyurea; after mixing 2,5-di(aminomethyl)furan and 2,2-bis-(4-glycolylaminophenyl)propane, N,N-dimethylformamide is added to dilute the mixture, and the mixture is heated to 60-80°C and stirred for 4-6 hours. After mixing evenly with the polyurea, 4,4'-di(maleimido)-1,1'-biphenyl is added, and the mixture is stirred at room temperature for 1-2 hours to obtain a modified polyurea; S2, uniformly mixing the modified polyurea with the anti-rust filler, dispersant, leveling agent and ultraviolet absorber; The molar ratio of the 4,4'-methylenebis(phenyl isocyanate) to polytetrahydrofuran and 1H-pyrrole-2,5-dimethylamine is 1:0.4-0.6:0.5-0.6; The molar ratio of the 2,5-bis(aminomethyl)furan to 2,2-bis-(4-glycolyloxyphenyl)propane and 4,4'-bis(maleimido)-1,1'-biphenyl is 1:1:3-4; The mass ratio of the modified polyurea to the anti-rust filler, the dispersant, the leveling agent and the ultraviolet absorber is 50-60:10-15:1-2:1-2:0.1-1.

2. The method for preparing the corrosion-resistant polyurea coating according to claim 1, characterized in that: The anti-rust filler is a mixture of one or more of mica iron oxide, zinc phosphate, aluminum phosphate, talcum powder, organic bentonite and titanium dioxide.

3. The method for preparing the corrosion-resistant polyurea coating according to claim 1, characterized in that: The dispersant is BYK-163.

4. The method for preparing the corrosion-resistant polyurea coating according to claim 1, characterized in that: The leveling agent is EFKA-3777.

5. The method for preparing the corrosion-resistant polyurea coating according to claim 1, characterized in that: The ultraviolet absorber is tinuvin 1130.

6. The method for preparing the corrosion-resistant polyurea coating according to claim 1, characterized in that: The method comprises the following steps, in parts by weight: S1. After mixing 25 parts of 4,4'-methylenebis(phenyl isocyanate) and 50 parts of polytetrahydrofuran, the mixture was heated to 80°C and stirred for 2 hours under a nitrogen atmosphere to obtain a prepolymer, and then 7.5 parts of 1H-pyrrole-2,5-dimethylamine was added. After stirring evenly, an equal volume of tetrahydrofuran was added to dilute the mixture, and stirring was continued for 6 hours to obtain polyurea; after mixing 12.6 parts of 2,5-bis(aminomethyl)furan and 34 parts of 2,2-bis-(4-glycolylaminophenyl)propane, an equal volume of N,N-dimethylformamide was added to dilute the mixture, and the mixture was heated to 60°C and stirred for 4 hours. After mixing evenly with the polyurea, 103.2 parts of 4,4'-bis(maleimido)-1,1'-biphenyl was added, and the mixture was stirred at room temperature for 2 hours to obtain a modified polyurea; S2. Mix 55 parts of modified polyurea, 15 parts of aluminum phosphate, 2 parts of BYK-163, 1 part of EFKA-3777 and 0.5 parts of tinuvin 1130 evenly to obtain the product.

7. A corrosion-resistant polyurea coating, characterized in that: Prepared by the method according to any one of claims 1 to 6.

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