A waterborne polyurethane for marine anticorrosive coating and a preparation method thereof

Abstract

The application provides a water-based polyurethane for ship anticorrosive paint and a preparation method thereof, and the water-based polyurethane comprises the following components: 130-250 parts by mass of self-made component A; 70-150 parts by mass of a polyisocyanate; 3-30 parts by mass of a first chain extender; 5-20 parts by mass of a second chain extender; and 3-15 parts by mass of a salting agent. The water-based polyurethane for ship anticorrosive paint and the preparation method thereof improve the corrosion resistance of the water-based polyurethane, improve the biodegradability of the product, and reduce the pollution to the environment.

Description

Technical Field

[0001] This invention belongs to the field of polymer synthesis technology, specifically relating to a waterborne polyurethane for marine anti-corrosion coatings and its preparation method. Background Technology

[0002] With increasingly stringent environmental protection and human health and safety requirements, the application space for solvent-based polyurethanes is shrinking. Waterborne polyurethanes, on the other hand, are a new type of polyurethane system that uses water instead of organic solvents as the dispersion medium; they are also known as water-dispersible polyurethanes, water-based polyurethanes, or water-based polyurethanes. Waterborne polyurethanes use water as a solvent and offer advantages such as being pollution-free, safe and reliable, possessing excellent mechanical properties, good compatibility, and ease of modification.

[0003] Waterborne polyurethane, with its environmentally friendly properties and ability to meet corrosion resistance requirements, is gradually replacing solvent-based polyurethane in marine anti-corrosion coatings. However, the presence of hydrophilic groups in waterborne polyurethane leads to poor water resistance of the coating film, resulting in poor long-term corrosion resistance, and its higher raw material costs limit its further application in marine anti-corrosion coatings. Summary of the Invention

[0004] This invention proposes a waterborne polyurethane for marine anti-corrosion coating and its preparation method, which greatly improves the corrosion resistance of waterborne polyurethane, reduces costs, improves the biodegradability of the product, and reduces environmental pollution.

[0005] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution.

[0006] This invention proposes a waterborne polyurethane for marine anti-corrosion coatings, comprising at least the following components:

[0007]

[0008] In one embodiment of the present invention, the self-made component A has a hydroxyl-terminated structure, and the average molecular weight of the self-made component A is 7000-9000.

[0009] In one embodiment of the present invention, the polyisocyanate includes one or a mixture of several of the following: toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, 1,6-hexane diisocyanate, phenylmethylene diisocyanate, naphthalene-1,5-diisocyanate, polymethylene polyphenyl isocyanate, tetramethylphenylmethylene diisocyanate, methylcyclohexyl diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, or dicyclohexylmethane diisocyanate.

[0010] In one embodiment of the present invention, the first chain extender comprises one or a mixture of several of the following: ethylene glycol, diethylene glycol, 1,4-butanediol, 2,3-butanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, glycerol, sorbitol, trimethylolpropane, or dimethylolcyclohexane.

[0011] In one embodiment of the present invention, the second chain extender includes one or a mixture of several of diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, N-propyldiethanolamine or tert-butyldiethanolamine.

[0012] In one embodiment of the present invention, the salt-forming agent includes one or a mixture of several of lactic acid, glacial acetic acid, glycolic acid or acetic anhydride.

[0013] This invention also proposes a method for preparing waterborne polyurethane for marine anti-corrosion coatings, comprising at least the following steps:

[0014] Preparation of self-made component A: 4-6 parts by weight of trimethylolpropane and 11-15 parts by weight of isocyanate were stirred and reacted at 70-80°C for 1 hour. Then 2-4 parts by weight of castor oil were added and stirred and reacted at 90-100°C for 2 hours. Then 2 parts by weight of cashew oil were added and stirred and reacted at 80-90°C for 2 hours to obtain self-made component A, which was then sealed and stored.

[0015] Preparation of waterborne polyurethane prepolymer: The self-made component A is heated to 45-55°C, polyisocyanate is added, the temperature is raised to 85-95°C and reacted for 1.5-2.5 h, the temperature is lowered to 45-55°C and the first chain extender and the first amount of acetone are added, the temperature is raised to 75-85°C and reacted for 1.5-3 h, the temperature is then lowered to 30-50°C and the second chain extender is added and reacted for 0.5-1.5 h, and finally the second amount of acetone is added to obtain the waterborne polyurethane prepolymer;

[0016] Preparation of waterborne polyurethane semi-finished product: A salting agent is added to the waterborne polyurethane prepolymer for neutralization reaction, and then deionized water is added while stirring. The amount of deionized water added is 2 to 4 times the mass of the solid in the waterborne polyurethane prepolymer to obtain the waterborne polyurethane semi-finished product.

[0017] Preparation of waterborne polyurethane resin: The waterborne polyurethane semi-finished product is subjected to vacuum distillation to remove acetone, thereby obtaining waterborne polyurethane resin.

[0018] In one embodiment of the present invention, the first content is 1 to 2 wt% of the total mass of solids in the reactants, and the second content is 25 to 35 wt% of the total mass of solids in the reactants.

[0019] In one embodiment of the present invention, the pressure of the vacuum distillation process is -0.09MPa to -0.1MPa.

[0020] This invention proposes a waterborne polyurethane for marine anti-corrosion coatings and its preparation method. The materials used are environmentally friendly and non-toxic, reducing costs and improving the biodegradability of the product, thereby mitigating environmental pollution and enhancing the safety of production workshops. It significantly improves the corrosion resistance of waterborne polyurethane, achieving performance comparable to solvent-based polyurethanes, and can be applied to marine anti-corrosion coatings. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a flowchart of a method for preparing a waterborne polyurethane for marine anti-corrosion coating according to the present invention.

[0023] Figure 2 This is a diagram showing the corrosion defects of polished steel plate No. 1 in this invention.

[0024] Figure 3 This is a diagram showing the corrosion defects of polished steel plate No. 2 in this invention.

[0025] Figure 4 This is a diagram showing the corrosion defects of polished steel plate No. 3 in this invention.

[0026] Figure 5 This is a diagram showing the corrosion defects of polished steel plate No. 4 in this invention.

[0027] Figure 6 This is a diagram showing the corrosion defects of the No. 5 polished steel plate in this invention.

[0028] Figure 7 This is a diagram showing the corrosion defects of polished steel plate No. 6 in this invention. Detailed Implementation

[0029] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0030] It should be understood that the invention can be embodied in various forms and should not be construed as being limited to the embodiments set forth herein. Rather, providing these embodiments will make the disclosure thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0031] This invention proposes a waterborne polyurethane for marine anti-corrosion coatings, comprising a self-made component A, a polyisocyanate, a first chain extender, and a salt-forming agent. The self-made component A is obtained by high-temperature reaction of a mixture of cashew nut oil, castor oil, and trimethylolpropane with isocyanate, and has a hydroxyl-terminated structure. The average molecular weight of the self-made component A is, for example, 7000–9000, and more specifically, 8000. In one embodiment of this invention, the content of the self-made component A is, for example, 130–250 parts by mass, the content of the polyisocyanate is, for example, 70–150 parts by mass, the content of the first chain extender is, for example, 3–30 parts by mass, the content of the second chain extender is, for example, 5–20 parts by mass, and the content of the salt-forming agent is, for example, 3–15 parts by mass.

[0032] In one embodiment of the present invention, the polyisocyanate includes, for example, one or a mixture of several selected from toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, 1,6-hexane diisocyanate, phenylenediamine diisocyanate, naphthalene-1,5-diisocyanate, polymethylene polyphenyl isocyanate, tetramethylphenylenediamine diisocyanate, methylcyclohexyl diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, or dicyclohexylmethane diisocyanate. The first chain extender includes, for example, one or a mixture of several selected from ethylene glycol, diethylene glycol, 1,4-butanediol, 2,3-butanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, glycerol, sorbitol, trimethylolpropane, or dimethylolcyclohexane. The second chain extender includes, for example, one or a mixture of several of diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, N-propyldiethanolamine, or tert-butyldiethanolamine. The salt-forming agent includes, for example, one or a mixture of several of lactic acid, glacial acetic acid, glycolic acid, or acetic anhydride.

[0033] Please see Figure 1 As shown, the present invention also proposes a method for preparing waterborne polyurethane for marine anti-corrosion coatings, including but not limited to steps S10-S40.

[0034] Step S10: Preparation of self-made component A: 4-6 parts by weight of trimethylolpropane and 11-15 parts by weight of isocyanate are stirred and reacted at 70-80°C for 1 hour. Then, 2-4 parts by weight of castor oil are added and stirred and reacted at 90-100°C for 2 hours. Then, 2 parts by weight of cashew oil are added and stirred and reacted at 80-90°C for 2 hours to obtain self-made component A, which is then sealed and stored.

[0035] Step S20: Preparation of waterborne polyurethane prepolymer: Heat self-made component A to 45-55°C, add polyisocyanate, heat to 85-95°C and react for 1.5-2.5 h, cool to 45-55°C and add the first chain extender and the first amount of acetone, then heat to 75-85°C and react for 1.5-3 h, then cool to 30-50°C and add the second chain extender and react for 0.5-1.5 h, finally add the second amount of acetone to obtain the waterborne polyurethane prepolymer.

[0036] Step S30: Preparation of waterborne polyurethane semi-finished product: Add a salting agent to the waterborne polyurethane prepolymer for neutralization reaction, then stir and add deionized water, and the amount of deionized water added is 2 to 4 times the mass of the solid in the waterborne polyurethane prepolymer to obtain the waterborne polyurethane semi-finished product.

[0037] Step S40: Preparation of waterborne polyurethane resin: The waterborne polyurethane semi-finished product is subjected to vacuum distillation to remove acetone and obtain waterborne polyurethane resin.

[0038] Please see Figure 1 As shown, in step S10, in one embodiment of the present invention, the isocyanate includes, for example, one or more of toluene diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, terephthalic diisocyanate, or isophorone diisocyanate. In one embodiment of the present invention, the stirring speed is set to, for example, 800-1000 r / min. In one embodiment of the present invention, the prepared self-made component A has a hydroxyl-terminated structure, and the average molecular weight of the self-made component A is, for example, 7000-9000, and further, the average molecular weight of the self-made component A is, for example, 8000.

[0039] Please see Figure 1 As shown, in step S20, in one embodiment of the present invention, the amount of self-made component A added is, for example, 130 to 250 parts by weight. In one embodiment of the present invention, the polyisocyanate includes, for example, one or a mixture of several selected from toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, 1,6-hexane diisocyanate, phenylenediamine diisocyanate, naphthalene-1,5-diisocyanate, polymethylene polyphenyl isocyanate, tetramethylphenylenediamine diisocyanate, methylcyclohexyl diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, or dicyclohexylmethane diisocyanate. The amount of polyisocyanate added is, for example, 70 to 150 parts by weight.

[0040] Please see Figure 1As shown, in step S20, in one embodiment of the present invention, the first chain extender includes, for example, one or a mixture of several of the following: ethylene glycol, diethylene glycol, 1,4-butanediol, 2,3-butanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, glycerol, sorbitol, trimethylolpropane, or dimethylolcyclohexane. The amount of the first chain extender added is, for example, 3 to 30 parts by mass, and the first content of acetone is, for example, 1 to 2 wt% of the total solid mass of the reactants at this time.

[0041] Please see Figure 1 As shown, in step S20, in one embodiment of the present invention, the second chain extender includes, for example, one or a mixture of several of diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, N-propyldiethanolamine, or tert-butyldiethanolamine. The salt-forming agent includes, for example, one or a mixture of several of lactic acid, glacial acetic acid, glycolic acid, or acetic anhydride. The amount of the second chain extender added is, for example, 5 to 20 parts by mass. After the reaction with the second chain extender, the isocyanate content (NCO value) in the reactants can be detected until the NCO reaches the theoretical value. Then, a second amount of acetone is added, and the second amount of acetone is, for example, 25 to 35 wt% of the total solid mass in the reactants at this point.

[0042] Please see Figure 1 As shown, in step S30, in one embodiment of the present invention, the salt-forming agent includes, for example, one or a mixture of several of lactic acid, glacial acetic acid, glycolic acid, or acetic anhydride. The amount of salt-forming agent added is, for example, 3 to 15 parts by mass. In one embodiment of the present invention, for example, the salt-forming agent is added to the aqueous polyurethane prepolymer, and a neutralization reaction is carried out at a stirring speed of 800 to 1000 r / min, and the neutralization reaction time is, for example, 1 to 2 min. Then, the stirring speed is adjusted to 1500 to 3000 r / min, and deionized water is added under these conditions, and the amount of deionized water added is, for example, 2 to 4 times the total mass of the solids in the aqueous polyurethane prepolymer. After the deionized water is added, the stirring speed is adjusted back to 800 to 1000 r / min, and stirring continues for 5 to 10 min to obtain an acetone-containing aqueous polyurethane semi-finished product.

[0043] Please see Figure 1 As shown, in step S40, in one embodiment of the present invention, the aqueous polyurethane semi-finished product is subjected to vacuum distillation to remove acetone, thereby obtaining aqueous polyurethane resin. The pressure of the vacuum distillation is set, for example, to -0.09 MPa to -0.1 MPa.

[0044] The technical solution of the present invention will be further described in detail below with reference to several embodiments and accompanying drawings. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] Example 1

[0046] Step S10: Preparation of homemade component A: 5 parts by mass of trimethylolpropane and 13 parts by mass of isocyanate are stirred and reacted at 75°C for 1 hour. Then, 3 parts by mass of castor oil are added and stirred and reacted at 100°C for 2 hours. Then, 2 parts by mass of cashew oil are added and stirred and reacted at 85°C for 2 hours to obtain homemade component A, which is then sealed and stored.

[0047] Step S20: Preparation of waterborne polyurethane prepolymer: Heat 150g of self-made component A to 45-55℃, add 100g of a mixture of isophorone diisocyanate, 1,6-hexanediisocyanate, and 4,4'-dicyclohexylmethane diisocyanate, raise the temperature to 85-95℃, and maintain the reaction at this temperature for 1.5-2.5h. Then lower the temperature to 45-55℃, add 10g of a mixture of glycerol and sorbitol, and at this time add 1.5wt% of acetone based on the total mass of solids in the reactants. Raise the temperature to 75-85℃ and react for 1.5-3h, then lower the temperature to 30-50℃, and at this time add 20g of diethanolamine and react for 0.5-1.5h until NCO reaches the theoretical preset value. Finally, add 30wt% of acetone based on the total mass of solids in the reactants to obtain the waterborne polyurethane prepolymer.

[0048] Step S30: Preparation of waterborne polyurethane semi-finished product: 12g of lactic acid is added to the waterborne polyurethane prepolymer for neutralization reaction, and then deionized water is added while stirring. The content of deionized water is 2.5 to 3.5 times the total mass of solids in the waterborne polyurethane prepolymer to obtain waterborne polyurethane semi-finished product containing acetone.

[0049] Step S40: Preparation of waterborne polyurethane resin: The waterborne polyurethane semi-finished product is subjected to vacuum distillation at -0.09MPa to -0.1MPa to remove acetone and obtain waterborne polyurethane resin.

[0050] Example 2

[0051] Step S10: Preparation of homemade component A: 4 parts by mass of trimethylolpropane and 11 parts by mass of isocyanate are stirred and reacted at 75°C for 1 hour. Then, 2 parts by mass of castor oil are added and stirred and reacted at 100°C for 2 hours. Then, 2 parts by mass of cashew oil are added and stirred and reacted at 85°C for 2 hours to obtain homemade component A, which is then sealed and stored.

[0052] Step S20: Preparation of waterborne polyurethane prepolymer: Heat 180g of self-made component A to 45-55℃, add 150g of a mixture of isophorone diisocyanate and diphenylmethane diisocyanate, raise the temperature to 85-95℃, and maintain the reaction at this temperature for 1.5-2.5h. Then lower the temperature to 45-55℃, add 28g of a mixture of diethylene glycol and 1,4-butanediol, and at this time add 1.5wt% acetone (based on the total mass of solids in the reactants). Raise the temperature to 75-85℃ and react for 1.5-3h, then lower the temperature to 30-50℃, and at this time add 12g of N-propyldiethanolamine and react for 0.5-1.5h until NCO reaches the theoretical preset value. Finally, add 30wt% acetone (based on the total mass of solids in the reactants) to obtain the waterborne polyurethane prepolymer.

[0053] Step S30: Preparation of waterborne polyurethane semi-finished product: Add 11g of glycolic acid to the waterborne polyurethane prepolymer for neutralization reaction, then stir and add deionized water. The content of deionized water is 2.5 to 3.5 times the total mass of solids in the waterborne polyurethane prepolymer to obtain waterborne polyurethane semi-finished product containing acetone.

[0054] Step S40: Preparation of waterborne polyurethane resin: The waterborne polyurethane semi-finished product is subjected to vacuum distillation at -0.09MPa to -0.1MPa to remove acetone and obtain waterborne polyurethane resin.

[0055] Example 3

[0056] Step S10: Preparation of homemade component A: 6 parts by mass of trimethylolpropane and 15 parts by mass of isocyanate are stirred and reacted at 75°C for 1 hour. Then, 4 parts by mass of castor oil are added and stirred and reacted at 100°C for 2 hours. Then, 2 parts by mass of cashew oil are added and stirred and reacted at 85°C for 2 hours to obtain homemade component A, which is then sealed and stored.

[0057] Step S20: Preparation of waterborne polyurethane prepolymer: Heat 225g of self-made component A to 45-55℃, add 145g of tetramethylphenyl dimethylene diisocyanate, raise the temperature to 85-95℃, and maintain the reaction at this temperature for 1.5-2.5h. Then lower the temperature to 45-55℃, add 25g of 1,4-butanediol, and at this time add 1.5wt% of acetone (based on the total mass of solids in the reactants). Raise the temperature to 75-85℃ and react for 1.5-3h, then lower the temperature to 30-50℃, and at this time add 10g of N-methyldiethanolamine and react for 0.5-1.5h until NCO reaches the theoretical preset value. Finally, add 30wt% of acetone (based on the total mass of solids in the reactants) to obtain the waterborne polyurethane prepolymer.

[0058] Step S30: Preparation of waterborne polyurethane semi-finished product: Add 15g of glacial acetic acid to the waterborne polyurethane prepolymer for neutralization reaction, then stir and add deionized water. The content of deionized water is 2.5 to 3.5 times the total mass of solids in the waterborne polyurethane prepolymer to obtain waterborne polyurethane semi-finished product containing acetone.

[0059] Step S40: Preparation of waterborne polyurethane resin: The waterborne polyurethane semi-finished product is subjected to vacuum distillation at -0.09MPa to -0.1MPa to remove acetone and obtain waterborne polyurethane resin.

[0060] Example 4

[0061] Step S10: Preparation of homemade component A: Mix 5 parts by mass of trimethylolpropane and 13 parts by mass of isocyanate at 80°C for 1 hour, then add 3 parts by mass of castor oil and mix at 100°C for 2 hours, then add 2 parts by mass of cashew oil and mix at 90°C for 2 hours to obtain homemade component A, and seal and store it.

[0062] Step S20: Preparation of waterborne polyurethane prepolymer: 150g of self-made component A is heated to 45-55℃, and 100g of isophorone diisocyanate, 10g of 1,6-hexanediisocyanate, and 20g of naphthalene-1,5-diisocyanate are added. The temperature is raised to 90℃ and maintained at this temperature for 2.5h. Then, the temperature is lowered to 45-55℃, and 20g of 1,4-butanediol is added. At this point, 1.5wt% of acetone (based on the total mass of solids in the reactants) is added. The temperature is raised to 80℃ and reacted for 3h. Then, the temperature is lowered to 30-50℃, and 12g of N-methyldiethanolamine is added and reacted for 0.5-1.5h until NCO reaches the theoretical preset value. Finally, 30wt% of acetone (based on the total mass of solids in the reactants) is added to obtain the waterborne polyurethane prepolymer.

[0063] Step S30: Preparation of waterborne polyurethane semi-finished product: Add 12g of glacial acetic acid to the waterborne polyurethane prepolymer for neutralization reaction, then stir and add deionized water. The content of deionized water is 2.5 to 3.5 times the total mass of solids in the waterborne polyurethane prepolymer to obtain waterborne polyurethane semi-finished product containing acetone.

[0064] Step S40: Preparation of waterborne polyurethane resin: The waterborne polyurethane semi-finished product is subjected to vacuum distillation at -0.09MPa to -0.1MPa to remove acetone and obtain waterborne polyurethane resin.

[0065] The waterborne polyurethane resin prepared according to this invention, along with other waterborne polyurethane resins, was coated onto a steel plate, and the corrosion resistance of the steel plate was tested. The test results are as follows: Figures 2 to 7 As shown.

[0066] The salt spray test was conducted according to GB / T 1771-1991 "Paints and Varnishes - Determination of Resistance to Neutral Salt Spray". The experimental equipment was a salt spray test chamber, and the experimental solution was a sodium chloride solution of (50±10) g / L, with a pH value of 6.5~7.2 at 25℃. The experimental samples were six polished steel plates with dimensions of 100mm×150mm.

[0067] One polished steel plate was completely immersed in the water-based polyurethane resin emulsion prepared in Example 1 of this invention, dried in a forced-air drying oven, and numbered 1. One polished steel plate was completely immersed in the water-based polyurethane resin emulsion prepared in Example 2 of this invention, dried in a forced-air drying oven, and numbered 2. Two polished steel plates were completely immersed in commercially available corrosion-resistant water-based polyurethane emulsion, dried in a forced-air drying oven, and numbered 3 and 4. The remaining two polished steel plates were left untreated as blank samples and numbered 5 and 6.

[0068] The six polished steel plates with different numbers were placed in a salt spray test chamber, with the temperature set at (23±2)℃ and the relative humidity at (50±5)%, and tested for 7 days. After the test, the six polished steel plates were removed, and the corrosion defects on the steel plate surface were observed. The test results are as follows: Figures 2 to 7 As shown.

[0069] Please see Figures 2 to 7 As shown, after 7 days of salt spray testing, steel plates without waterborne polyurethane emulsion impregnation exhibit numerous corrosion defects on their surface. While the corrosion defects were somewhat improved with commercially available corrosion-resistant waterborne polyurethane emulsion impregnation, the corrosion remained severe. However, the steel plates treated with the waterborne polyurethane resin emulsion prepared in this invention showed significantly reduced surface corrosion defects and a much smaller corrosion area, demonstrating the excellent corrosion resistance of the waterborne polyurethane resin prepared in this invention.

[0070] In summary, this invention proposes a waterborne polyurethane for marine anti-corrosion coatings and its preparation method. A primary molecular weight product is prepared by reacting cashew oil, castor oil, and trimethylolpropane with isocyanate. This product exhibits high crosslinking degree and strong resistance to salt spray and chemicals. Furthermore, using vegetable oils as raw materials makes it environmentally friendly and non-toxic, reducing costs, improving biodegradability, mitigating environmental pollution, and enhancing the safety of the production workshop. By using this product as a raw material to synthesize high molecular weight waterborne polyurethane, the corrosion resistance of the waterborne polyurethane is significantly improved, comparable to that of solvent-based polyurethanes, making it suitable for application in marine anti-corrosion coatings.

[0071] The above description is merely a preferred embodiment of this application and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to the technical solutions formed by a specific combination of the above-mentioned technical features, but should also cover other technical solutions formed by any combination of the above-mentioned technical features or their equivalent features without departing from the inventive concept. For example, technical solutions formed by replacing the above-mentioned features with technical features with similar functions disclosed in this application (but not limited to) each other.

[0072] Apart from the technical features described in the specification, the other technical features are known to those skilled in the art. To highlight the innovative features of this invention, the other technical features will not be described in detail here.

Claims

1. A waterborne polyurethane for marine anti-corrosion coating, characterized in that, It includes at least the following components: Self-made component A: 130~250 parts by weight; 70-150 parts by weight of polyisocyanate; 3-30 parts by weight of the first chain extender; 5-20 parts by weight of the second chain extender; as well as Salt-forming agent: 3-15 parts by weight; The self-made component A is obtained by high-temperature reaction of a mixture of cashew oil, castor oil, and trimethylolpropane with isocyanate. The self-made component A has a hydroxyl-terminated structure and an average molecular weight of 7000-9000. To prepare the self-made component A, 4-6 parts by weight of trimethylolpropane and 11-15 parts by weight of isocyanate are first stirred and reacted at 70-80°C for 1 hour. Then, 2-4 parts by weight of castor oil are added and stirred and reacted at 90-100°C for 2 hours. Finally, 2 parts by weight of cashew oil are added and stirred and reacted at 80-90°C for 2 hours to obtain the self-made component A, which is then sealed and stored.

2. The waterborne polyurethane for marine anti-corrosion coating according to claim 1, characterized in that, The polyisocyanate includes one or a mixture of several of the following: toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, 1,6-hexane diisocyanate, phenylmethylene diisocyanate, naphthalene-1,5-diisocyanate, polymethylene polyphenyl isocyanate, tetramethylphenylmethylene diisocyanate, methylcyclohexyl diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, or dicyclohexylmethane diisocyanate.

3. The waterborne polyurethane for marine anti-corrosion coating according to claim 1, characterized in that, The first chain extender includes one or a mixture of several of the following: ethylene glycol, diethylene glycol, 1,4-butanediol, 2,3-butanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, glycerol, sorbitol, trimethylolpropane, or dimethylolcyclohexane.

4. The waterborne polyurethane for marine anti-corrosion coating according to claim 1, characterized in that, The second chain extender includes one or a mixture of several of diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, N-propyldiethanolamine or tert-butyldiethanolamine.

5. The waterborne polyurethane for marine anti-corrosion coating according to claim 1, characterized in that, The salt-forming agent includes one or a mixture of several of lactic acid, glacial acetic acid, glycolic acid, or acetic anhydride.

6. A method for preparing a waterborne polyurethane for marine anti-corrosion coatings as described in any one of claims 1-5, characterized in that, At least the following steps are included: Preparation of self-made component A: 4-6 parts by weight of trimethylolpropane and 11-15 parts by weight of isocyanate were stirred and reacted at 70-80°C for 1 hour. Then 2-4 parts by weight of castor oil were added and stirred and reacted at 90-100°C for 2 hours. Then 2 parts by weight of cashew oil were added and stirred and reacted at 80-90°C for 2 hours to obtain self-made component A, which was then sealed and stored. Preparation of waterborne polyurethane prepolymer: The self-made component A is heated to 45~55℃, polyisocyanate is added, the temperature is raised to 85~95℃ and reacted for 1.5~2.5h, the temperature is lowered to 45~55℃ and the first chain extender and the first amount of acetone are added, the temperature is raised to 75~85℃ and reacted for 1.5~3h, then the temperature is lowered to 30~50℃ and the second chain extender is added and reacted for 0.5~1.5h, and finally the second amount of acetone is added to obtain the waterborne polyurethane prepolymer; Preparation of waterborne polyurethane semi-finished product: A salting agent is added to the waterborne polyurethane prepolymer for neutralization reaction, and then deionized water is added while stirring. The amount of deionized water added is 2 to 4 times the mass of the solid in the waterborne polyurethane prepolymer to obtain the waterborne polyurethane semi-finished product. Preparation of waterborne polyurethane resin: The waterborne polyurethane semi-finished product is subjected to vacuum distillation to remove acetone, thereby obtaining waterborne polyurethane resin.

7. The method for preparing waterborne polyurethane for marine anti-corrosion coating according to claim 6, characterized in that, The first content is 1 to 2 wt% of the total mass of solids in the reactants, and the second content is 25 to 35 wt% of the total mass of solids in the reactants.

8. The method for preparing waterborne polyurethane for marine anti-corrosion coating according to claim 6, characterized in that, The pressure of the vacuum distillation process is -0.09 MPa to -0.1 MPa.

9. The method for preparing waterborne polyurethane for marine anti-corrosion coating according to claim 6, characterized in that, In the preparation step of the self-made component A, the stirring speed is 800~1000 r / min.

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