Wear-resistant waterborne polyurethane finish paint and preparation method thereof

Abstract

The invention relates to the technical field of coatings, and discloses a wear-resistant waterborne polyurethane finish paint and a preparation method thereof. The wear-resistant waterborne polyurethane finish paint comprises a component A and a component B in a mass ratio of (4-7): 1, the component A is prepared from the following components in parts by mass: 50 to 60 parts of waterborne polyurethane, 10 to 15 parts of hyperbranched polysiloxane, 2 to 3 parts of polyoxyethylene fatty acid, 0.8 to 1.2 parts of a de-foaming agent, 6 to 8 parts of color paste and 10 to 15 parts of water; and the component B comprises an isocyanate curing agent. The wear-resistant waterborne polyurethane finish paint prepared in the invention has excellent adhesion strength and wear resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of coatings, and specifically to a wear-resistant waterborne polyurethane topcoat and a preparation method thereof. Background Art

[0002] Polyurethane topcoats have excellent mechanical properties, chemical resistance, and adjustable flexibility, and are often used as common industrial coatings in fields such as airplanes and high-speed rails; among them, although traditional polyurethane topcoats have excellent properties, they contain volatile organic compounds, which are harmful to the environment and human health; therefore, waterborne polyurethane coatings have gradually replaced traditional solvent-based coatings and become a research hotspot due to their advantages such as non-toxicity and non-flammability.

[0003] In the prior art, since the hardness and crosslinking of waterborne polyurethane are usually weaker than those of solvent-based polyurethane, when it is used on the surface of automobiles, etc., firstly, there are defects such as poor wear resistance, resulting in premature wear and loss of gloss of the paint surface, reducing the service life; secondly, the interfacial bonding force between the waterborne polyurethane and the substrate is weak, and problems such as coating peeling and edge corrosion are likely to occur; thus reducing its practical applicability and making it difficult to meet the requirements of high-end application scenarios; in addition, nano-fillers are usually introduced, but there are problems such as poor dispersibility and weak interfacial properties, which are instead not conducive to the improvement of comprehensive performance.

[0004] In summary, to solve the above problems, it is of great significance to prepare a wear-resistant waterborne polyurethane topcoat. Summary of the Invention

[0005] The purpose of the present invention is to provide a wear-resistant waterborne polyurethane topcoat and a preparation method thereof to solve the problems raised in the prior art.

[0006] To achieve the above purpose, the present invention provides the following technical solutions: A wear-resistant waterborne polyurethane topcoat, the wear-resistant waterborne polyurethane topcoat comprises component A and component B with a mass ratio of (4~7):1; component A comprises the following components: by mass, 50~60 parts of waterborne polyurethane, 10~15 parts of hyperbranched polysiloxane, 2~3 parts of fatty acid polyoxyethylene ester, 0.8~1.2 parts of defoamer, 6~8 parts of color paste, 10~15 parts of water; component B comprises an isocyanate curing agent.

[0007] Preferably, the preparation method of the waterborne polyurethane is: mix isophorone diisocyanate, part of low molecular weight polyethylene glycol, 2,2-dimethylolpropionic acid, and part of the catalyst, and stir and react at 80~85°C for 1~2 hours; add the remaining part of low molecular weight polyethylene glycol, isocyanato nano-silica, and the remaining part of the catalyst and continue to react for 3~4 hours; cool down to 65~70°C, add a composite chain extender, stir for 2~3 hours, cool down to 35~40°C, and adjust the pH to 7~9 with triethylamine to obtain waterborne polyurethane.

[0008] Preferably, the raw materials of the aqueous polyurethane include the following components: by mass, 25 to 26 parts of isophorone diisocyanate, 50 to 64 parts of low molecular weight polyethylene glycol, 2 to 4 parts of 2,2-dimethylolpropionic acid, 0.2 to 0.5 part of catalyst, 5 to 8 parts of isocyano-functionalized nano-silica, and 1 to 3 parts of composite chain extender.

[0009] Preferably, the average molecular weight of the low molecular weight polyethylene glycol is 400 to 600.

[0010] Preferably, for the isocyano-functionalized nano-silica, its preparation method is as follows: (1) Disperse vinyltrimethoxysilane in an ethanol aqueous solution, heat to 60 to 70 °C and stir for 1 to 2 hours, add nano-silica, and stir and react for 4 to 6 hours; add mercapto polyethylene glycol amine and water-soluble azo initiator, heat to 75 to 80 °C, and continue to stir for 6 to 7 hours; wash and dry to obtain modified nano-silica; (2) Add the modified nano-silica, isophorone diisocyanate, and triethylamine to DMF in sequence, stir at room temperature for 1 to 2 hours, filter and dry to obtain isocyano-functionalized nano-silica.

[0011] Preferably, in the raw materials of the modified nano-silica, the following components are included: by mass fraction, 10 parts of nano-silica, 1 to 2 parts of vinyltrimethoxysilane, 2.5 to 3.5 parts of mercapto polyethylene glycol amine, and 0.1 to 0.12 part of water-soluble azo initiator; In the raw materials of the isocyano-functionalized nano-silica, the mass ratio of the modified nano-silica, isophorone diisocyanate, and triethylamine is 10:5 to 7:0.2.

[0012] Preferably, the composite chain extender includes 1,4-butanediol and 2,2,3,3,4,4-hexafluoropentane-1,5-diol with a mass ratio of 1:1.

[0013] Preferably, the preparation method of the hyperbranched polysiloxane is as follows: uniformly mix γ-glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, trifluoropropyltrimethoxysilane, deionized water, and absolute ethanol, add hydrochloric acid solution to adjust the pH to 5 to 6, stir at 60 to 70 °C for 5 to 6 hours, and vacuum dry to obtain hyperbranched polysiloxane.

[0014] Preferably, the raw materials of the hyperbranched polysiloxane include the following components: by mass, 5 to 7 parts of γ-glycidoxypropyltrimethoxysilane, 5 to 7 parts of γ-methacryloxypropyltrimethoxysilane, 0.3 to 0.5 part of trifluoropropyltrimethoxysilane, 10 to 12 parts of deionized water, and 25 to 30 parts of absolute ethanol.

[0015] Preferably, the following operating steps are included: Step 1: Add hyperbranched polysiloxane and fatty acid polyoxyethylene ester into water and mix evenly for 30 to 40 minutes, then add waterborne polyurethane, defoamer, and color paste and continue to mix for 20 to 30 minutes to obtain Component A; Step 2: When in use, evenly mix Component B with Component A to obtain the wear-resistant waterborne polyurethane topcoat.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: In this application, based on waterborne polyurethane containing nanoparticles and introducing hyperbranched polysiloxane, a crosslinked network is effectively formed, synergistically improving the adhesion and wear resistance of the wear-resistant waterborne polyurethane topcoat.

[0017] Among them, to achieve the dispersibility and interfacial properties in the nanoparticle topcoat, it is pre-grafted in waterborne polyurethane to improve the wear resistance and adhesion of waterborne polyurethane and enhance the adhesion. At the same time, in order to be evenly dispersed in waterborne polyurethane, a multi-step modification strategy is adopted: First, vinyl groups are introduced onto the surface of silica through a vinyl silane coupling agent, then thiol-terminated polyethylene glycol amine is grafted through a thiol-ene click reaction, and finally isocyanato-functionalized nano-silica is obtained by reacting the amino group with isophorone diisocyanate; after such directional modification and then introducing it into the polyurethane chain segment, random grafting is avoided, ensuring that all nanoparticles can form stable chemical bonds with the polyurethane matrix.

[0018] Among them, low molecular weight polyethylene glycol and isophorone diisocyanate are selected to react in waterborne polyurethane to introduce hydrophilic groups and active end groups to form a stable skeleton; while enhancing the network structure, it can effectively relieve the rigid stress concentration of nano-silica; and it has a similar chain segment to the modified nano-silica and has similar compatibility. It should be noted that: the molecular weight of polyethylene glycol should not be too high. The chain segment of high molecular weight PEG is long, and the intermolecular entanglement is serious, resulting in a significant increase in the viscosity of the prepolymer, making stirring and dispersion difficult and affecting the uniformity of the reaction; and the hydrophilicity of PEG is too strong (especially when the molecular weight is high), which will introduce too many ether bonds (-O-), increasing the water absorption rate of the coating, resulting in a decrease in water resistance and reducing the wear resistance of polyurethane.

[0019] In addition, fluorine groups are introduced into the chain extender and hyperbranched polysiloxane of the present invention; these hydrophobic groups form a microphase separation structure with the hydrophilic polyethylene glycol chain segments, not only retaining the hydrophilic processing performance of the coating, but also significantly reducing the moisture absorption rate; at the same time, the dendritic structure of hyperbranched polysiloxane not only helps to reduce the interfacial energy, but also can form an energy dissipation network inside the coating to effectively relieve stress concentration.

[0020] At the coating-substrate interface, the polyethylene glycol segments on the surface of modified nano-silica significantly improve wettability and permeability, while hyperbranched polysiloxane synergistically optimizes the interfacial bonding with fatty acid polyoxyethylene ester through interfacial migration; enabling the coating to exhibit excellent adhesion on various substrates; inside the coating, isocyanato nano-silica serves as a multi-functional crosslinking point, jointly constructing a three-dimensional network structure with the polyurethane main chain and chain extender, greatly enhancing the adhesion and abrasion resistance of the coating. Detailed implementation manners

[0021] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0022] In the following detailed implementation manners, parts are by mass. In this embodiment, it should be noted that there are no special restrictions on the purchase manufacturers of all raw materials involved in the present invention. Exemplarily, the CAS number of γ-glycidoxypropyltrimethoxysilane is 2530-83-8; the CAS number of γ-methacryloxypropyltrimethoxysilane is 2530-85-0; the CAS number of trifluoropropane trimethoxysilane is 429-60-7; the CAS number of 2,2'-azobis(2-methyl-N-(2-hydroxyethyl)propionamide) (water-soluble azo initiator) is 61551-69-7; the CAS number of 2,2-dimethylolpropionic acid is 4767-03-7; the CAS number of 1,4-butanediol is 110-63-4; the CAS number of hexafluoropentanediol is 376-90-9; the product number of mercapto polyethylene glycol amine is X-GF-0038; the CAS number of vinyltrimethoxysilane is 2768-02-7; the product number of nano-silica is XH-SiO2-50, with a large number of unsaturated residual bonds and hydroxyl groups in different bonding states on the surface; the CAS number of dibutyltin dilaurate is 77-58-7; the model of fatty acid polyoxyethylene ester is industrial grade, and the product number is fxy2012; the model of the defoaming agent is BYK024; the molecular weights of polyethylene glycol are 600 and 2000; the CAS number of isophorone diisocyanate is 4098-71-9.

[0023] The preparation method of hyperbranched polysiloxane is as follows: uniformly mix 5 parts of γ-glycidoxypropyltrimethoxysilane, 5 parts of γ-methacryloxypropyltrimethoxysilane, 0.3 part of trifluoropropane trimethoxysilane, 12 parts of deionized water, and 30 parts of absolute ethanol, add 2 mol of hydrochloric acid solution to adjust the pH to 5-6, stir at 60-70 °C for 5-6 hours, and dry in vacuum to obtain hyperbranched polysiloxane.

[0024] Example 1: A preparation method of a wear-resistant waterborne polyurethane topcoat, comprising the following operating steps: Step 1: Add 10 parts of hyperbranched polysiloxane and 2 parts of fatty acid polyoxyethylene ester into 12 parts of water, mix evenly for 30 minutes, add 50 parts of waterborne polyurethane, 0.8 part of defoamer, and 7 parts of color paste, and continue to mix for 30 minutes to obtain Component A; Step 2: Uniformly mix Component B with Component A to obtain a wear-resistant waterborne polyurethane topcoat; the mass ratio of Component A to Component B is 6:1; Among them, the preparation method of waterborne polyurethane is: mix 28 parts of isophorone diisocyanate, 50 parts of low molecular weight polyethylene glycol, 3 parts of 2,2-dimethylolpropionic acid, and 0.2 part of catalyst, and stir and react at 85 °C for 2 hours; add 10 parts of low molecular weight polyethylene glycol, 8 parts of isocyano nano-silica, and 0.15 part of catalyst, and continue to react for 3-4 hours; cool down to 70 °C, add 2 parts of a composite chain extender (1,4-butanediol and hexafluoropentanediol with a mass ratio of 1:1), stir for 3 hours, cool down to 40 °C, and adjust the pH to 8.5 with triethylamine to obtain waterborne polyurethane; The preparation method of isocyano nano-silica is: (1) Disperse 1.5 parts of vinyltrimethoxysilane in an ethanol aqueous solution, heat up to 70 °C, stir for 2 hours, add 10 parts of nano-silica, and stir and react for 4 hours; add 3 parts of mercapto polyglycol amino and 0.12 part of water-soluble azo initiator, heat up to 80 °C, and continue to stir for 6 hours; wash and dry to obtain modified nano-silica; (2) Add the modified nano-silica, isophorone diisocyanate, and triethylamine to DMF in sequence, stir at room temperature for 1-2 hours, filter and dry to obtain isocyano nano-silica; among them, the mass ratio of modified nano-silica, isophorone diisocyanate, and triethylamine is 10:6.5:0.2.

[0025] Example 2: A preparation method of a wear-resistant waterborne polyurethane topcoat, comprising the following operating steps: Step 1: Add 15 parts of hyperbranched polysiloxane and 2 parts of fatty acid polyoxyethylene ester into 12 parts of water, mix evenly for 30 minutes, add 60 parts of waterborne polyurethane, 0.8 part of defoamer, and 7 parts of color paste, and continue to mix for 30 minutes to obtain Component A; Step 2: Uniformly mix Component B with Component A to obtain a wear-resistant waterborne polyurethane topcoat; the mass ratio of Component A to Component B is 6:1; Among them, the preparation method of the aqueous polyurethane is as follows: Mix 28 parts of isophorone diisocyanate, 50 parts of low molecular weight polyethylene glycol, 3 parts of 2,2-dimethylolpropionic acid, and 0.2 part of a partial catalyst, and stir and react at 85°C for 2 hours; add 10 parts of low molecular weight polyethylene glycol, 8 parts of isocyano-functionalized nano-silica, and 0.15 part of a catalyst and continue to react for 3 to 4 hours; cool down to 70°C, add 2 parts of a composite chain extender (1,4-butanediol and hexafluoropentanediol with a mass ratio of 1:1), stir for 3 hours, cool down to 40°C, and adjust the pH to 8.5 with triethylamine to obtain the aqueous polyurethane; The preparation method of the isocyano-functionalized nano-silica is as follows: (1) Disperse 1.5 parts of vinyltrimethoxysilane in an ethanol aqueous solution, heat up to 70°C and stir for 2 hours, add 10 parts of nano-silica, and stir and react for 4 hours; add 3 parts of mercapto polyethylene glycol amine and 0.12 part of a water-soluble azo initiator, heat up to 80°C, and continue to stir for 6 hours; wash and dry to obtain modified nano-silica; (2) Add the modified nano-silica, isophorone diisocyanate, and triethylamine to DMF in sequence, stir at room temperature for 1 to 2 hours, filter and dry to obtain the isocyano-functionalized nano-silica; among them, the mass ratio of the modified nano-silica, isophorone diisocyanate, and triethylamine is 10:6.5:0.2.

[0026] Example 3: A preparation method of a wear-resistant aqueous polyurethane topcoat, comprising the following operating steps: Step 1: Add 10 parts of hyperbranched polysiloxane and 3 parts of fatty acid polyoxyethylene ester to 12 parts of water, mix evenly for 30 minutes, add 60 parts of aqueous polyurethane, 0.8 part of defoamer, and 7 parts of color paste, and continue to mix for 30 minutes to obtain Component A; Step 2: Uniformly mix Component B and Component A to obtain the wear-resistant aqueous polyurethane topcoat; the mass ratio of Component A and Component B is 6:1; Among them, the preparation method of the aqueous polyurethane is as follows: Mix 28 parts of isophorone diisocyanate, 50 parts of low molecular weight polyethylene glycol, 3 parts of 2,2-dimethylolpropionic acid, and 0.2 part of a partial catalyst, and stir and react at 85°C for 2 hours; add 10 parts of low molecular weight polyethylene glycol, 8 parts of isocyano-functionalized nano-silica, and 0.15 part of a catalyst and continue to react for 3 to 4 hours; cool down to 70°C, add 2 parts of a composite chain extender (1,4-butanediol and hexafluoropentanediol with a mass ratio of 1:1), stir for 3 hours, cool down to 40°C, and adjust the pH to 8.5 with triethylamine to obtain the aqueous polyurethane; The preparation method of isocyano nano-silica is as follows: (1) Disperse 1.5 parts of vinyltrimethoxysilane in an ethanol aqueous solution, heat up to 70 °C and stir for 2 hours, add 10 parts of nano-silica, and stir and react for 4 hours; add 3 parts of mercapto poly(ethylene glycol) amine and 0.12 part of water-soluble azo initiator, heat up to 80 °C, and continue to stir for 6 hours; wash and dry to obtain modified nano-silica; (2) Add the modified nano-silica, isophorone diisocyanate, and triethylamine to DMF in sequence, stir at room temperature for 1-2 hours, filter and dry to obtain isocyano nano-silica; among them, the mass ratio of the modified nano-silica, isophorone diisocyanate, and triethylamine is 10:6.5:0.2.

[0027] Comparative Example 1 is based on Example 2, and the molecular weight of polyethylene glycol is increased. Step 1: Add 15 parts of hyperbranched polysiloxane and 2 parts of fatty acid polyoxyethylene ester to 12 parts of water, mix evenly for 30 minutes, add 60 parts of waterborne polyurethane, 0.8 part of defoamer, and 7 parts of color paste, and continue to mix for 30 minutes to obtain Component A; Step 2: Uniformly mix Component B and Component A to obtain a wear-resistant waterborne polyurethane topcoat; the mass ratio of Component A and Component B is 6:1. Among them, the preparation method of waterborne polyurethane is: mix 28 parts of isophorone diisocyanate, 50 parts of high molecular weight polyethylene glycol (molecular weight of 2000), 3 parts of 2,2-dimethylolpropionic acid, and 0.2 part of partial catalyst, and stir and react at 85 °C for 2 hours; add 10 parts of high molecular weight polyethylene glycol (molecular weight of 2000), 8 parts of isocyano nano-silica, and 0.15 part of catalyst, and continue to react for 3 hours; cool down to 70 °C, add 2 parts of composite chain extender, stir for 3 hours, cool down to 40 °C, and adjust the pH to 8.5 with triethylamine to obtain waterborne polyurethane. The preparation method of isocyano nano-silica is as follows: (1) Disperse 1.5 parts of vinyltrimethoxysilane in an ethanol aqueous solution, heat up to 70 °C and stir for 2 hours, add 10 parts of nano-silica, and stir and react for 4 hours; add 3 parts of mercapto poly(ethylene glycol) amine and 0.12 part of water-soluble azo initiator, heat up to 80 °C, and continue to stir for 6 hours; wash and dry to obtain modified nano-silica; (2) Add the modified nano-silica, isophorone diisocyanate, and triethylamine to DMF in sequence, stir at room temperature for 2 hours, filter and dry to obtain isocyano nano-silica; among them, the mass ratio of the modified nano-silica, isophorone diisocyanate, and triethylamine is 10:6.5:0.2.

[0028] Comparative Example 2 is based on Example 2, and fluorine groups are not introduced into the waterborne polyurethane and hyperbranched polysiloxane. Step 1: Add 10 parts of hyperbranched polysiloxane and 2 parts of fatty acid polyoxyethylene ester into 12 parts of water, mix evenly for 30 minutes, then add 50 - 60 parts of waterborne polyurethane, 0.8 part of defoamer, and 7 parts of color paste, and continue to mix for 30 minutes to obtain Component A; Step 2: Mix Component B and Component A evenly to obtain a wear-resistant waterborne polyurethane topcoat; The mass ratio of Component A to Component B is 6:1; Among them, the preparation method of waterborne polyurethane is as follows: Mix 28 parts of isophorone diisocyanate, 50 parts of low molecular weight polyethylene glycol, 3 parts of 2,2-dimethylolpropionic acid, and 0.2 part of partial catalyst, and stir and react at 85°C for 2 hours; Add 10 parts of low molecular weight polyethylene glycol, 8 parts of isocyano nano-silica, and 0.15 part of catalyst, and continue to react for 3 - 4 hours; Cool down to 70°C, add 2 parts of 1,4-butanediol, stir for 3 hours, cool down to 40°C, and adjust the pH to 8.5 with triethylamine to obtain waterborne polyurethane; The preparation method of isocyano nano-silica is as follows: (1) Disperse 1.5 parts of vinyltrimethoxysilane in an ethanol aqueous solution, heat up to 70°C, stir for 2 hours, add 10 parts of nano-silica, and stir and react for 4 hours; Add 3 parts of mercapto polyethylene glycol amine and 0.12 part of water-soluble azo initiator, heat up to 80°C, and continue to stir for 6 hours; Wash and dry to obtain modified nano-silica; (2) Add the modified nano-silica, isophorone diisocyanate, and triethylamine to DMF in sequence, stir at room temperature for 2 hours, filter and dry to obtain isocyano nano-silica; Among them, the mass ratio of the modified nano-silica, isophorone diisocyanate, and triethylamine is 10:6.5:0.2; Among them, the preparation method of hyperbranched polysiloxane is as follows: Mix 5 parts of γ-glycidyl ether oxypropyltrimethoxysilane, 5 parts of γ-methacryloxypropyltrimethoxysilane, 12 parts of deionized water, and 30 parts of absolute ethanol evenly, add 2 mol of hydrochloric acid solution to adjust the pH to 5.5, stir at 70°C for 5 hours, and dry in vacuum to obtain hyperbranched polysiloxane.

[0029] Comparative Example 3 is based on Example 2, and isocyano nano-silica is prepared with isophorone diisocyanate; Step 1: Add 10 parts of hyperbranched polysiloxane and 2 parts of fatty acid polyoxyethylene ester into 12 parts of water, mix evenly for 30 minutes, then add 50 - 60 parts of waterborne polyurethane, 0.8 part of defoamer, and 7 parts of color paste, and continue to mix for 30 minutes to obtain Component A; Step 2: Mix Component B and Component A evenly to obtain a wear-resistant waterborne polyurethane topcoat; The mass ratio of Component A to Component B is 6:1; Among them, the preparation method of the aqueous polyurethane is as follows: Mix 28 parts of isophorone diisocyanate, 50 parts of low molecular weight polyethylene glycol, 3 parts of 2,2-dimethylolpropionic acid, and 0.2 part of partial catalyst, and stir and react at 85 °C for 2 hours; add 10 parts of low molecular weight polyethylene glycol, 8 parts of isocyano-functionalized nano-silica, and 0.15 part of catalyst and continue to react for 3 to 4 hours; cool down to 70 °C, add 2 parts of a composite chain extender (1,4-butanediol and hexafluoropentanediol with a mass ratio of 1:1), stir for 3 hours, cool down to 40 °C, and adjust the pH to 8.5 with triethylamine to obtain the aqueous polyurethane; The preparation method of the isocyano-functionalized nano-silica is as follows: Weigh isophorone diisocyanate and nano-silica according to a mass ratio of 1.5:0.2; add the nano-silica to 50 parts of toluene and 100 parts of petroleum ether and ultrasonically disperse, heat up to 95 °C and reflux for 1.5 hours, add 0.02 part of dibutyltin dilaurate, under nitrogen protection, add isophorone diisocyanate and stir for 5 hours, cool to room temperature, filter and wash to obtain the isocyano-functionalized nano-silica.

[0030] Comparative Example 4 is based on Example 2, without adding hyperbranched polysiloxane; Step 1: Add 2 parts of fatty acid polyoxyethylene ester to 12 parts of water and mix evenly for 30 minutes, add 60 parts of aqueous polyurethane, 0.8 part of defoamer, and 7 parts of color paste and continue to mix for 30 minutes to obtain Component A; Step 2: Uniformly mix Component B and Component A to obtain a wear-resistant aqueous polyurethane topcoat; the mass ratio of Component A to Component B is 6:1; Among them, the preparation method of the aqueous polyurethane is as follows: Mix 28 parts of isophorone diisocyanate, 50 parts of low molecular weight polyethylene glycol, 3 parts of 2,2-dimethylolpropionic acid, and 0.2 part of partial catalyst, and stir and react at 85 °C for 2 hours; add 10 parts of low molecular weight polyethylene glycol, 8 parts of isocyano-functionalized nano-silica, and 0.15 part of catalyst and continue to react for 3 to 4 hours; cool down to 70 °C, add 2 parts of a composite chain extender (1,4-butanediol and hexafluoropentanediol with a mass ratio of 1:1), stir for 3 hours, cool down to 40 °C, and adjust the pH to 8.5 with triethylamine to obtain the aqueous polyurethane; The preparation method of the isocyano-functionalized nano-silica is as follows: (1) Disperse 1.5 parts of vinyltrimethoxysilane in an ethanol aqueous solution, heat up to 70 °C and stir for 2 hours, add 10 parts of nano-silica, and stir and react for 4 hours; add 3 parts of mercapto poly(ethylene glycol) amine and 0.12 part of water-soluble azo initiator, heat up to 80 °C, and continue to stir for 6 hours; wash and dry to obtain modified nano-silica; (2) Add the modified nano-silica, isophorone diisocyanate, and triethylamine to DMF in sequence, stir at room temperature for 1 to 2 hours, filter and dry to obtain the isocyano-functionalized nano-silica; among them, the mass ratio of the modified nano-silica, isophorone diisocyanate, and triethylamine is 10:6.5:0.2.

[0031] Detection test: The waterborne polyurethane topcoats prepared in Examples 1 to 3 and Comparative Examples 1 to 4 were uniformly coated on a metal plate (100 mm × 100 mm × 3 mm) and cured, and the thickness of each coating was 20 μm; the following tests were carried out: (1) Detect the adhesion of Examples 1 to 3 and Comparative Examples 1 to 4 according to the GB / T286 2021 standard; (2) Immerse in tertiary water for 240 hours and then dry; then according to GB / T1768-2006 "Determination of abrasion resistance of paints and varnishes - Rotating rubber wheel method", 6 standard specimens were made from Examples 1 to 3 and Comparative Examples 1 to 4 respectively, and the wear values of the 6 standard specimens in each group of samples were recorded. After removing the maximum and minimum wear values, the remaining average wear value was calculated to detect the abrasion resistance of the samples.

[0032] Table 1 Adhesion Average wear value (mg) Example 1 Grade 0 15.2 Example 2 Grade 0 14.3 Example 3 Grade 0 14.7 Comparative Example 1 Grade 0 15.8 Comparative Example 2 Grade 0 17.4 Comparative Example 3 Grade 1 16.5 Comparative Example 4 Grade 2 18.2 Conclusion: Based on Example 2, Comparative Example 1 increased the molecular weight of polyethylene glycol; this led to a decline in the performance of the waterborne polyurethane topcoat; because the chain segments of high molecular weight PEG are longer and the intermolecular entanglement is serious, resulting in a significant increase in the viscosity of the prepolymer, making stirring and dispersion difficult and affecting the reaction uniformity; based on Example 2, Comparative Example 2 did not introduce fluorine groups into the waterborne polyurethane and hyperbranched polysiloxane; this led to a decrease in the water resistance of the waterborne polyurethane topcoat, thus resulting in a decline in the performance of the waterborne polyurethane topcoat; based on Example 2, Comparative Example 3 prepared isocyanato-nano-silica with isophorone diisocyanate; this led to an increase in the rigidity of isocyanato-nano-silica, restricting the movement of chain segments; the surface of silica was pre-modified with a silane coupling agent to introduce a definite reactive group (vinyl), and then an amino group was introduced through a thiol-vinyl reaction to ensure that the isocyanate group only reacts with the amino group, avoiding random grafting, and improving the interfacial compatibility of silica and alleviating the rigidity; thus resulting in a decline in the performance of the waterborne polyurethane prepared in Comparative Example 3; based on Example 2, Comparative Example 4 did not add hyperbranched polysiloxane; this led to a decrease in the adhesion and abrasion resistance of the waterborne polyurethane.

[0033] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention.

Claims

1. A wear-resistant waterborne polyurethane topcoat, characterized in that: The wear-resistant waterborne polyurethane topcoat comprises component A and component B with a mass ratio of (4 - 7):1; Component A comprises the following components: by mass parts, 50 - 60 parts of waterborne polyurethane, 10 - 15 parts of hyperbranched polysiloxane, 2 - 3 parts of fatty acid polyoxyethylene ester, 0.8 - 1.2 parts of defoamer, 6 - 8 parts of color paste, 10 - 15 parts of water; Component B comprises an isocyanate curing agent.

2. The preparation method of a wear-resistant waterborne polyurethane topcoat according to claim 1, characterized in that: The preparation method of the waterborne polyurethane is as follows: Mix isophorone diisocyanate, part of low molecular weight polyethylene glycol, 2,2-dimethylolpropionic acid, and part of the catalyst, and stir and react at 80 - 85 °C for 1 - 2 hours; Add the remaining part of low molecular weight polyethylene glycol, isocyanato nano-silica, and the remaining part of the catalyst and continue to react for 3 - 4 hours; Cool down to 65 - 70 °C, add a composite chain extender, stir for 2 - 3 hours, cool down to 35 - 40 °C, and adjust the pH to 7 - 9 with triethylamine to obtain waterborne polyurethane.

3. The preparation method of a wear-resistant waterborne polyurethane topcoat according to claim 2, characterized in that: The raw materials of the waterborne polyurethane comprise the following components: by mass parts, 25 - 26 parts of isophorone diisocyanate, 50 - 64 parts of low molecular weight polyethylene glycol, 2 - 4 parts of 2,2-dimethylolpropionic acid, 0.2 - 0.5 parts of catalyst, 5 - 8 parts of isocyanato nano-silica, 1 - 3 parts of composite chain extender.

4. The preparation method of a wear-resistant waterborne polyurethane topcoat according to claim 2, characterized in that: The average molecular weight of the low molecular weight polyethylene glycol is 400 - 600.

5. The preparation method of a wear-resistant waterborne polyurethane topcoat according to claim 2, characterized in that: For the isocyanato nano-silica, its preparation method is as follows: (1) Disperse vinyltrimethoxysilane in an ethanol aqueous solution, heat up to 60 - 70 °C and stir for 1 - 2 hours, add nano-silica, and stir and react for 4 - 6 hours; Add mercapto polyethylene glycol amine and a water-soluble azo initiator, heat up to 75 - 80 °C, and continue to stir for 6 - 7 hours; Wash and dry to obtain modified nano-silica; (2) Add the modified nano-silica, isophorone diisocyanate, and triethylamine to DMF in sequence, stir at room temperature for 1 - 2 hours, filter and dry to obtain isocyanato nano-silica.

6. The preparation method of a wear-resistant waterborne polyurethane topcoat according to claim 5, characterized in that: In the raw materials of the modified nano-silica, it comprises the following components: by mass fraction, 10 parts of nano-silica, 1 - 2 parts of vinyltrimethoxysilane, 2.5 - 3.5 parts of mercapto polyethylene glycol amine, 0.1 - 0.12 parts of water-soluble azo initiator; In the raw materials of the isocyanato nano-silica, the mass ratio of the modified nano-silica, isophorone diisocyanate, and triethylamine is 10:5 - 7:0.

2.

7. The preparation method of a wear-resistant waterborne polyurethane topcoat according to claim 2, characterized in that: The composite chain extender comprises 1,4-butanediol and hexafluoropentanediol with a mass ratio of 1:

1.

8. The preparation method of a wear-resistant waterborne polyurethane topcoat according to claim 1, characterized in that: The preparation method of the hyperbranched polysiloxane is as follows: Uniformly mix γ-glycidyletheroxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, trifluoropropane trimethoxysilane, deionized water, and absolute ethanol, add hydrochloric acid solution to adjust the pH to 5 - 6, stir at 60 - 70 °C for 5 - 6 hours, and dry in vacuum to obtain hyperbranched polysiloxane.

9. The preparation method of a wear-resistant waterborne polyurethane topcoat according to claim 8, characterized in that: The raw materials of the hyperbranched polysiloxane include the following components: by mass parts, 5 to 7 parts of γ-glycidyletheroxypropyltrimethoxysilane, 5 to 7 parts of γ-methacryloxypropyltrimethoxysilane, 0.3 to 0.5 parts of trifluoropropane trimethoxysilane, 10 to 12 parts of deionized water, and 25 to 30 parts of absolute ethanol.

10. The preparation method of a wear-resistant waterborne polyurethane topcoat according to claim 1, characterized in that: It includes the following operation steps: Step 1: Add the hyperbranched polysiloxane and fatty acid polyoxyethylene ester into water and mix evenly for 30 to 40 minutes, then add waterborne polyurethane, defoamer, and color paste and continue to mix for 20 to 30 minutes to obtain Component A; Step 2: When in use, evenly mix Component B and Component A to obtain the wear-resistant waterborne polyurethane topcoat.