High performance waterborne polyurethane composition and method of making

Abstract

The application discloses a kind of high-performance water-based polyurethane compositions and preparation method, the composition is composed of the following weight parts components: high-performance water-based polyurethane emulsion 90~95 parts;Nano alumina 0.3~0.5 parts;Grinding aid 0.06~0.1 parts;Leveling agent 1.4~7.4 parts;Anti-scratching aid 1~2 parts;Water-based thickening agent 1~2 parts.Preparation, measured nano alumina and grinding aid are added to a certain amount of deionized water, grind thoroughly, after cooling to normal temperature, measured high-performance water-based polyurethane emulsion, leveling agent, anti-scratching aid, water-based thickening agent are sequentially added in stirring state, fully stir, 300 mesh filter screen filters, package as high-performance water-based polyurethane composition.This composition is better on paint panel Leveling, film strong and transparent, antioxidant, anti-scratching, relative to TPU film Stealth car clothes, simple construction, cost is lower, to irregular surface is better.

Description

TECHNICAL FIELD

[0001] The present invention relates to the field of waterborne polyurethane technology, in particular to high performance waterborne polyurethane compositions. BACKGROUND

[0002] Automobiles are basically stored in the open air after production, and bird droppings can have a serious impact on the paint, so it is necessary to paste a protective film to ensure that the paint is not damaged when delivered to the customer; in addition, although the surface of the paint on the automobile has high hardness, it is inevitable that scratches will occur during use, affecting the appearance, although this can be solved by polishing or repainting, but this increases the maintenance cost and time cost.

[0003] The invisible car cover product launched by 3M Company is to coat pressure-sensitive adhesive on TPU film, and then paste the TPU film on the surface of the vehicle body, relying on the elasticity and scratch resistance of the TPU film to solve the above problems. The TPU film is relatively soft and can be pasted on curved surfaces, but because it is soft, it is very difficult to paste; the peeling force between the pressure-sensitive adhesive and the paint is very large and almost impossible to peel off, and once the vehicle needs to be repaired, the TPU film needs to be removed, causing the paint on the part where the TPU film is pasted to be damaged, resulting in increased losses.

[0004] With the increase in the number of automobiles, it is imperative to develop a paint protection film that is easy to apply, inexpensive, easy to maintain, and environmentally friendly.

[0005] Protecting the paint does not mean damaging the appearance of the paint or changing the color of the paint, so the paint protection film must first maintain transparency, good gloss, and good weather resistance under any temperature conditions; in terms of material selection, materials with good structural symmetry should not be used to prevent opacity due to crystallization; the compatibility of the components must be good to prevent a decrease in the transparency of the material due to poor compatibility. Second, the protective film must have sufficient strength, and for polyurethane materials, the simplest method is to increase the bond energy, such as increasing the urea bond, i.e., using amine chain extenders instead of alcohol chain extenders. Third, the protective film must be resistant to yellowing, i.e., using aliphatic materials. Fourth, the protective film must be resistant to scratching, and polyurethane materials have good scratch resistance due to their high elastic deformation and high strength after film formation. Further introduction of scratch-resistant components can greatly improve the scratch resistance of polyurethane materials and truly protect the paint. Fifth, the ease of application, spraying is undoubtedly the most convenient method of application, and the appearance is good, but the basic requirement for spraying is that the nozzle cannot be blocked, and it is best to pass through a 300-mesh filter, and it must have a suitable kinematic viscosity, i.e., anti-sagging performance. Sixth, the paint must maintain an appropriate peeling force for easy maintenance.

[0006] It can be seen that providing a paint protection film that meets the above performance requirements is a problem that needs to be solved in the art. SUMMARY

[0007] In view of the problems existing in the prior art, the purpose of this invention is to provide a paint protection film solution that is easy to use, has stable and reliable performance, and is suitable for paint protection of automobiles at the factory and for paint protection of users in daily use.

[0008] To achieve the above objectives, the present invention provides a high-performance waterborne polyurethane composition comprising the following components in parts by weight:

[0009]

[0010] Furthermore, the oligomer polyol of the high-performance polyurethane emulsion is a mixture of polyether polyol, polytetrahydrofuran ether diol (PTMEG), and hydroxyl fluorosilicone oil. PTMEG is preferably 3-methyl polytetrahydrofuran ether diol (3-methylPTMEG) with a molecular weight of 1400 or 2000.

[0011] Furthermore, the hydroxyl fluorosilicone oil in the high-performance polyurethane emulsion is an oligomer of trifluoropropylmethylsiloxane.

[0012] Furthermore, the high-performance polyurethane emulsion resin molecular segments contain urea bonds formed by 3,3′-dimethyl-4,4′-diaminodicyclohexylmethane and isocyanate:

[0013]

[0014] Wherein, R represents the main chain of a high-performance polyurethane emulsion resin.

[0015] Furthermore, the molecular segments of the high-performance polyurethane emulsion resin contain methoxysilane structures:

[0016]

[0017] Wherein, R represents the main chain of a high-performance polyurethane emulsion resin.

[0018] Furthermore, the nano-alumina is a γ-phase crystal with a particle size of 10–20 nm;

[0019] Furthermore, the grinding aid is a mixture of dimethylethanolamine and acetylenic diol in a mass ratio of 9 / 1.

[0020] Furthermore, the leveling agent is an organosilicon leveling agent; the anti-scratch additive is an organosilicon anti-scratch additive; and the water-based thickener is preferably an associative thickener.

[0021] To achieve the above objectives, the present invention provides a method for preparing the above-mentioned high-performance waterborne polyurethane composition, comprising:

[0022] (1) Add the measured amount of nano aluminum oxide and grinding aid to a certain amount of deionized water, grind thoroughly, and cool to room temperature;

[0023] (2) Add the measured amounts of high-performance waterborne polyurethane emulsion, leveling agent, anti-scratch agent and waterborne thickener in sequence while stirring, and stir thoroughly.

[0024] (3) Filter screen filtration, packaged as a high-performance waterborne polyurethane composition.

[0025] Furthermore, the preparation process of the high-performance waterborne polyurethane emulsion is as follows:

[0026] (11) Add the measured amount of 3-methylPTMEG and hydroxy fluorosilicone oil into the reactor, heat to 110-120℃, dehydrate under vacuum of 0.095 or less for 2 hours, and after depressurization, add the measured amount of dry dimethylolbutyric acid (DMBA) between 100-110℃. After the dimethylolbutyric acid is completely dissolved, cool down to 70-80℃.

[0027] (12) Add measured amounts of isoflurane diisocyanate (IPDI) and antioxidant 1010, react at 83-87°C for 1 hour, then add catalyst XK-651 and 120 ppm of 3-methylPTMEG, continue the reaction for 2 hours, and cool down to 60-65°C.

[0028] (13) Add acetone to dilute the excess amount of 3,3′-dimethyl-4,4′-diaminodicyclohexylmethane, maintain the reaction at this temperature for 90 min, and then cool down to 45-50℃.

[0029] (14) Add an appropriate amount of acetone to dilute, add 90% of the molar amount of triethylamine of DMBA to neutralize, and neutralize for 10 min;

[0030] (15) Add the measured amount of deionized water at 10-15℃, start the emulsifier to emulsify, and emulsify for 10 minutes;

[0031] (16) Add the measured amount of isoflurane diamine, N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane and diethylenetriamine diluted with deionized water, and continue emulsifying for 5 min;

[0032] (17) Stop emulsification, slowly raise the temperature to 48-52°C, stir at this temperature for 30 minutes, and remove acetone under vacuum.

[0033] (18) Filter, discharge, and package for later use as a high-performance polyurethane emulsion.

[0034] The high-performance polyurethane composition prepared by this invention is safe and environmentally friendly, easy to apply, and its performance meets or exceeds that of TPU film products. The preparation method of this invention is simple and easy to implement, the raw materials are readily available, the process is highly controllable, the product quality is stable, and the application is easy. Detailed Implementation

[0035] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further explained below with reference to specific examples.

[0036] This solution, taking into account the usage environment of the car wrap, presents a high-performance waterborne polyurethane composition. This composition is made by synthesizing a high-performance waterborne polyurethane emulsion, adding abrasion-resistant and scratch-resistant additives and other auxiliaries. It can be diluted with deionized water, and the VOC emissions during the drying process are less than 2%. When used, this composition is applied to the surface of painted panels by spraying or brushing. It can be heated or naturally dried to form a film without damaging the painted panel, providing excellent protection for the painted surface. This composition has good leveling properties on painted panels, and the film is tough, transparent, oxidation-resistant, and scratch-resistant. Compared to TPU film car wraps, it is simpler to apply, lower in cost, and has better adhesion to irregular surfaces.

[0037] Accordingly, the high-performance waterborne polyurethane composition provided in this scheme is mainly composed of the following components in parts by weight:

[0038]

[0039] In the synthesis of the high-performance polyurethane emulsion in this component, the oligomer polyol used is a mixture of polyether polyol polytetrahydrofuran ether diol (PTMEG) and hydroxyl fluorosilicone oil. PTMEG is preferably 3-methyl polytetrahydrofuran ether diol (3-methylPTMEG), which can ensure that the film will not crystallize at low temperatures and affect the transparency. The molecular weight is preferably 1400 or 2000.

[0040] The preferred hydroxyl fluorosilicone oil used is an oligomer of trifluoropropylmethylsiloxane, preferably a product with a hydroxyl value of 95-100 mgKOH / g; the mass ratio of 3-methylPTMEG to hydroxyl fluorosilicone oil is 100 / 5.

[0041] Furthermore, the molecular segments of this high-performance polyurethane emulsion resin contain urea bonds formed by 3,3′-dimethyl-4,4′-diaminodicyclohexylmethane and isocyanate:

[0042]

[0043] Wherein, R represents the main chain of a high-performance polyurethane emulsion resin.

[0044] Furthermore, the molecular segments of this high-performance polyurethane emulsion resin contain methoxysilane structures:

[0045]

[0046] Wherein, R represents the main chain of a high-performance polyurethane emulsion resin.

[0047] Based on this, this solution also provides specific formulations with synergistic effects:

[0048] The preferred nano-alumina is the γ-phase crystal form with a particle size of 10–20 nm.

[0049] The grinding aid is a mixture of dimethylethanolamine and acetylenol, preferably the long-chain linear polymer Surfadol 541. The mass ratio of dimethylethanolamine to Surfadol 541 is 9 / 1, and the amount added is 20% of the mass of aluminum oxide.

[0050] The preferred leveling agent is a silicone leveling agent, preferably BYK 333; the preferred anti-scratch additive is a silicone anti-scratch additive, preferably Dow Corning DC 51; the preferred water-based thickener is an associative thickener, preferably [brand name missing]. 299.

[0051] The present invention also provides a corresponding preparation method for a high-performance waterborne polyurethane composition composed of the above components in the corresponding proportions. The preparation method includes the following two steps:

[0052] Step 1: Synthesize high-performance waterborne polyurethane emulsion.

[0053] A measured amount of 3-methylPTMEG and hydroxyl fluorosilicone oil were added to a reactor. The mixture was heated to 110–120°C and dehydrated under a vacuum of less than 0.095 for 2 hours. After depressurization, a measured amount of dried dimethylolbutyric acid (DMBA) was added between 100–110°C. Once the DMBA was completely dissolved, the temperature was lowered to 70–80°C, and a measured amount of isoflurane diisocyanate (IPDI) and antioxidant 1010 were added. The mixture was reacted at 83–87°C for 1 hour. Then, catalyst XK-651 was added at 120 ppm of 3-methylPTMEG, and the reaction was continued for 2 hours. The temperature was lowered to 60–65°C, and acetone was added to dilute the measured amount of 3,3′-dimethyl-4,4′-dimethylolbutyric acid. - Diaminodicyclohexylmethane was reacted at this temperature for 90 minutes, then cooled to 45-50°C. An appropriate amount of acetone was added for dilution, followed by neutralization with 90% of the molar amount of triethylamine (DMBA). After neutralization for 10 minutes, a measured amount of deionized water at 10-15°C was added, and the emulsifier was started for emulsification. After emulsification for 10 minutes, a measured amount of isoflurane diamine, N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane, and diethylenetriamine diluted with deionized water were added. Emulsification was continued for 5 minutes, then emulsification was stopped. The temperature was slowly raised to 48-52°C, and stirred at this temperature for 30 minutes. Acetone was removed under vacuum, and the mixture was filtered, discharged, and packaged for later use as a high-performance polyurethane emulsion.

[0054] Step 2: Preparation of high-performance waterborne polyurethane composition

[0055] A measured amount of nano-alumina and grinding aid are added to a certain amount of deionized water, ground thoroughly, and cooled to room temperature. Then, measured amounts of high-performance waterborne polyurethane emulsion, silicone leveling agent, anti-scratch aid, and waterborne thickener are added sequentially while stirring. The mixture is stirred thoroughly, filtered through a 300-mesh filter, and packaged as a high-performance waterborne polyurethane composition.

[0056] The high-performance waterborne polyurethane composition prepared in this way has its peel strength on the paint surface adjusted by the amount of silicone leveling agent added. The polyurethane prepared using asymmetric 3-methylPTMEG has significantly lower crystallinity than that prepared using ordinary PTMEG, thus providing better transparency, especially at low temperatures. In this scheme, 3,3′-dimethyl-4,4′-diaminodicyclohexylmethane is used as a chain extender, resulting in polyurethane with superior mechanical properties.

[0057] The introduction of hydroxyl fluorosilicone oil into this high-performance waterborne polyurethane composition improves the hydrophobicity of the waterborne polyurethane film while ensuring compatibility, thus enhancing its weather resistance. The methoxysilane structure introduced in this scheme can form a coupling structure with inorganic aluminum oxide, improving the dispersibility of aluminum oxide and enhancing the scratch resistance of the film formed by this composition.

[0058] Therefore, this high-performance waterborne polyurethane composition has good leveling and no sagging when sprayed onto the paint surface. After drying and forming a film, the peel force on the paint surface is adjustable from 400 to 1000 g / 25 mm, the tensile strength is greater than 30 MPa, the elongation is greater than 600%, there is no scratch after wiping with a 1 kg load of steel wool 10 times, the transparency is greater than 90%, the haze is less than 5%, and the surface tension is less than 50 dynes.

[0059] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments, unless specific conditions are specified, are generally determined according to national standards. If no corresponding national standard exists, then common international standards, conventional conditions, or conditions recommended by the manufacturer are followed. Unless otherwise stated, all parts are parts by weight, all percentages are weight percentages, and polymer molecular weights are number average molecular weights.

[0060] Unless otherwise defined or stated, all technical and scientific terms used herein have the same meaning as are familiar to those skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be used in the methods of this invention.

[0061] 1. High-performance waterborne polyurethane emulsion

[0062] Example 1.1:

[0063] 200 kg of 3-methylPTMEG (molecular weight 2000) and 10 kg of hydroxyl fluorosilicone oil were added to a reactor and dehydrated at 110–120 °C under a vacuum of less than 0.095 for 2 hours. After depressurization, 14.8 kg of dried DMBA was added at 100–110 °C. Once the DMPA was completely dissolved, the temperature was lowered to 70–80 °C, and 79 kg of IPDI and 200 g of antioxidant 1010 were added. The reaction was carried out at 83–87 °C for 1 hour, and then 24 g of catalyst XK was added. -651°C, continue the reaction for 2 hours, cool to 60-65°C, add acetone to dilute 11.9 kg of 3,3′-dimethyl-4,4′-diaminodicyclohexylmethane, maintain this temperature for 90 min, cool to 45-50°C, add an appropriate amount of acetone for dilution, add 9.09 kg of triethylamine for neutralization, neutralize for 10 min, add 443 kg of 10-15°C deionized water, start the emulsifier for emulsification, emulsify for 10 min, add 50 kg of... 9.7 kg of isophorone diamine, 2.95 kg of N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane, and 0.5 kg of diethylenetriamine were diluted with deionized water at 10–15 °C. The mixture was emulsified for another 5 min, then the emulsification was stopped. The temperature was slowly raised to 48–52 °C, and the mixture was stirred at this temperature for 30 min. Acetone was removed under vacuum to obtain a light blue semi-transparent emulsion. The emulsion was then filtered, discharged, and packaged for later use as a high-performance waterborne polyurethane emulsion.

[0064] Example 1.2:

[0065] 210 kg of 3-methylPTMEG (molecular weight 1400) and 10.5 kg of hydroxyl fluorosilicone oil were added to a reactor. The mixture was heated to 110–120 °C and dehydrated under a vacuum of less than 0.095 for 2 hours. After depressurization, 22.2 kg of dried DMBA was added between 100–110 °C. Once the DMPA was completely dissolved, the temperature was lowered to 70–80 °C, and 103 kg of IPDI and 210 g of antioxidant 1010 were added. The mixture was then heated to 83– The reaction was carried out at 87℃ for 1 hour, then 25.2 g of catalyst XK-651 was added, and the reaction continued for 2 hours. The temperature was then lowered to 60-65℃, and 12.4 kg of 3,3′-dimethyl-4,4′-diaminodicyclohexylmethane was diluted with acetone. The reaction was maintained at this temperature for 90 minutes, then the temperature was lowered to 45-50℃, and an appropriate amount of acetone was added for dilution. 13.6 kg of triethylamine was added for neutralization, and the neutralization was carried out for 10 minutes. Finally, 464 kg of [unspecified substance] was added. Emulsify with deionized water at 10-15℃ using an emulsifier for 10 minutes. Then add 10.3 kg of isoflurane diamine, 3.1 kg of N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane, and 0.6 kg of diethylenetriamine diluted with 60 kg of deionized water at 10-15℃. Continue emulsifying for 5 minutes, then stop emulsifying and slowly raise the temperature to 48-52℃. Stir at this temperature for 30 minutes, then remove acetone under vacuum to obtain a light blue semi-transparent emulsion. Filter, discharge, and package for later use as a high-performance waterborne polyurethane emulsion.

[0066] 2. High-performance polyurethane compositions

[0067] Example 2.1

[0068] 0.5 kg of nano-alumina and 0.1 kg of grinding aid were added to 10.0 kg of deionized water and ground thoroughly. After cooling to room temperature, 90.0 kg of the high-performance waterborne polyurethane emulsion prepared in Example 1.1, 7.4 kg of BYK-333, and 1.0 kg of DC-51 were added sequentially while stirring. 299 1.0Kg, thoroughly stirred, filtered through a 300-mesh filter, and packaged as a high-performance waterborne polyurethane composition.

[0069] This composition, when sprayed onto a paint surface, exhibits good leveling and no sagging. After drying and forming a film, it has a peel strength of 450g / 25mm, a tensile strength greater than 32MPa, an elongation of 750%, and shows no scratches after being rubbed 10 times with a 1kg load of steel wool. It also has a transparency of 91%, a haze of 4%, and a surface tension of 43 dynes.

[0070] Example 2.2

[0071] 0.5 kg of nano-alumina and 0.1 kg of grinding aid were added to 10.0 kg of deionized water and ground thoroughly. After cooling to room temperature, 95.0 kg of the high-performance waterborne polyurethane emulsion prepared in Example 1.1, 1.4 kg of BYK-333, and 1.0 kg of DC-51 were added sequentially while stirring. 299 2.0Kg, thoroughly stirred, filtered through a 300-mesh filter, and packaged as a high-performance waterborne polyurethane composition.

[0072] This composition, when sprayed onto a paint surface, exhibits good leveling and no sagging. After drying and forming a film, it has a peel strength of 1000g / 25mm, a tensile strength greater than 34MPa, an elongation of 830%, and shows no scratches after being rubbed 10 times with a 1kg load of steel wool. It also has a transparency of 91.4%, a haze of 3.7%, and a surface tension of 45 dynes.

[0073] Example 2.3

[0074] 0.3 kg of nano-alumina and 0.06 kg of grinding aid were added to 6.0 kg of deionized water and ground thoroughly. After cooling to room temperature, 90.0 kg of the high-performance waterborne polyurethane emulsion prepared in Example 1.2, 6.64 kg of BYK-333, and 2.0 kg of DC-51 were added sequentially while stirring. 299 1.0Kg, thoroughly stirred, filtered through a 300-mesh filter, and packaged as a high-performance waterborne polyurethane composition.

[0075] This composition, when sprayed onto a paint surface, exhibits good leveling and no sagging. After drying and forming a film, it has a peel strength of 650g / 25mm, a tensile strength greater than 37MPa, an elongation of 610%, and shows no scratches after being rubbed 10 times with a 1kg load of steel wool. It also has a transparency of 91%, a haze of 3.9%, and a surface tension of 47 dynes.

[0076] Example 2.4

[0077] 0.4 kg of nano-alumina and 0.08 kg of grinding aid were added to 8.0 kg of deionized water and ground thoroughly. After cooling to room temperature, 95.0 kg of the high-performance waterborne polyurethane emulsion prepared in Example 1.2, 1.52 kg of BYK-333, and 2.0 kg of DC-51 were added sequentially while stirring. 299 1.0Kg, thoroughly stirred, filtered through a 300-mesh filter, and packaged as a high-performance waterborne polyurethane composition.

[0078] This composition, when sprayed onto a paint surface, exhibits good leveling and no sagging. After drying and forming a film, it has a peel strength of 850g / 25mm, a tensile strength greater than 38MPa, an elongation of 560%, and shows no scratches after being rubbed 10 times with a 1kg load of steel wool. It also has a transparency of 90.8%, a haze of 4.1%, and a surface tension of 48 dynes.

[0079] Example 2.5

[0080] 0.5 kg of nano-alumina and 0.1 kg of grinding aid were added to 10.0 kg of deionized water and ground thoroughly. After cooling to room temperature, 90.0 kg of the high-performance waterborne polyurethane emulsion prepared in Example 1.2, 7.4 kg of BYK-333, and 1.0 kg of DC-51 were added sequentially while stirring. 299 1.0Kg, thoroughly stirred, filtered through a 300-mesh filter, and packaged as a high-performance waterborne polyurethane composition.

[0081] This composition, when sprayed onto a paint surface, exhibits good leveling and no sagging. After drying and forming a film, it has a peel strength of 400g / 25mm, a tensile strength greater than 39MPa, an elongation of 590%, and shows no scratches after being rubbed 10 times with a 1kg load of steel wool. It also has a transparency of 91.5%, a haze of 3.7%, and a surface tension of 44 dynes.

[0082] As can be seen from the above examples, the composition solution given by the present invention has good leveling on painted panels, and the adhesive film is tough, transparent, antioxidant, and scratch-resistant. Compared with TPU film for car wraps, it is simple to apply, has a lower cost, and has better adhesion to irregular surfaces.

[0083] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A high-performance waterborne polyurethane composition, characterized in that, It consists of the following components in parts by weight: 90-95 parts of high-performance waterborne polyurethane emulsion; 0.3–0.5 parts of nano-alumina; Grinding aid 0.06–0.1 parts; Leveling agent: 1.4–7.4 parts; 1-2 parts of anti-scratch additive; 1-2 parts of water-based thickener; The high-performance polyurethane emulsion contains oligomeric polyols, wherein the oligomeric polyols are a mixture of polytetrahydrofuran ether diol and hydroxyl fluorosilicone oil, wherein the hydroxyl fluorosilicone oil is an oligomer of trifluoropropylmethylsiloxane, and the hydroxyl value of the oligomer of trifluoropropylmethylsiloxane is 95-100 mgKOH / g. The high-performance waterborne polyurethane emulsion resin molecular segments contain urea bonds formed by 3,3′-dimethyl-4,4′-diaminodicyclohexylmethane and isocyanate: Wherein, R is the main chain of high-performance waterborne polyurethane emulsion resin; The high-performance waterborne polyurethane emulsion resin molecular segments contain methoxysilane structures: Wherein, R represents the main chain of a high-performance waterborne polyurethane emulsion resin.

2. The waterborne polyurethane composition according to claim 1, characterized in that, The nano-alumina is in the γ-phase crystal form with a particle size of 10–20 nm.

3. The waterborne polyurethane composition according to claim 1, characterized in that, The grinding aid is a mixture of dimethylethanolamine and acetylenic diol in a mass ratio of 9 / 1.

4. The waterborne polyurethane composition according to claim 1, characterized in that, The leveling agent is an organosilicon leveling agent; the anti-scratch additive is an organosilicon anti-scratch additive; and the water-based thickener is preferably an associative thickener.

5. A method for preparing a high-performance waterborne polyurethane composition according to any one of claims 1-4, characterized in that, include: (1) Add the measured amount of nano-alumina and grinding aid to a certain amount of deionized water, grind thoroughly, and cool to room temperature; (2) Add the measured amounts of high-performance waterborne polyurethane emulsion, leveling agent, anti-scratch agent and waterborne thickener in sequence while stirring, and stir thoroughly; (3) Filter screen filtration, packaged as a high-performance waterborne polyurethane composition.

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