Self-cleaning waterborne polyurethane, preparation method and application thereof

Abstract

The application relates to the paint production field and discloses a self-cleaning water-based polyurethane and a preparation method and application thereof, the self-cleaning water-based polyurethane is prepared by mixing a hexanedioic acid polyester polyol, a fluorine-containing dihydric alcohol, an aliphatic diisocyanate, a phosphorus-containing dihydric alcohol and a pre-chain extender solution, heating, carrying out a polymerization reaction under nitrogen protection, adding a neutralizer to carry out a neutralization reaction after cooling, adding water to carry out dispersion emulsification, adding ethylenediamine to carry out a post-chain extension reaction, filtering and obtaining the self-cleaning water-based polyurethane; the fluorine-containing dihydric alcohol is used for preparing the polyurethane, the polyurethane is endowed with stronger hydrophobicity, and the self-cleaning effect is realized.

Description

Technical Field

[0001] This application relates to the field of coating production technology, and in particular to a self-cleaning waterborne polyurethane, its preparation method, and its application. Background Technology

[0002] In 1937, Otto Bayer first studied polyurethane (PU) as a coating material. In recent years, due to its excellent properties, PU has been successfully applied in various fields such as coatings, adhesives, elastomers, and synthetic leather. The main chain of PU contains a large number of repeating structural units, urethane (-NHCOO-), making it a class of polymeric materials with different soft and hard segment structures. Polyurethane is obtained through stepwise polymerization reactions of soft segments (polyethers and polyester polyols) and hard segments (polyisocyanates, chain extenders, and end-capping agents). Soft segments generally have good flexibility; the more soft segments there are, the better the elasticity and flexibility of PU. Furthermore, soft segments contribute to PU's thermal stability and other properties. The hard segment structure has strong intermolecular chain forces, with tightly packed molecular chains forming high-modulus hard segment regions, providing PU with strength and modulus properties. The functional groups in the hard segments determine the hydrophilicity, hydrophobicity, heat resistance, and chemical stability of PU. The performance characteristics of polyurethane largely depend on the ratio and structure of soft and hard segments. In practical applications, different functional polyurethane materials can be prepared by selecting different soft and hard segments through complex molecular structure design, thereby meeting the needs of different fields.

[0003] However, the linear structure of waterborne polyurethane (WPU) molecules and the presence of numerous hydrophilic groups on the chains limit their application in the coatings field.

[0004] The problem this solution aims to solve is: how to provide a method for preparing waterborne polyurethane with good hydrophobic properties to achieve self-cleaning capabilities. Summary of the Invention

[0005] The purpose of this application is to provide a method for preparing a waterborne polyurethane with self-cleaning ability. The polyurethane is prepared by using a fluorinated diol. Since fluorine is the most electronegative element, the carbon-fluorine bond (CF) has high bond energy and the molecular chains are tightly arranged, forming a low surface energy surface, which makes it difficult for water molecules to wet. In addition, fluorine gives the polyurethane stronger resistance to acids, alkalis and solvents, and prevents the surface from losing its hydrophobicity due to corrosion failure.

[0006] To achieve the above objectives, this application discloses a method for preparing a self-cleaning waterborne polyurethane. The self-cleaning waterborne polyurethane is prepared by mixing an adipic acid-based polyester polyol, a fluorinated diol, an aliphatic diisocyanate, a phosphorus-containing diol, and a pre-chain extender solution, heating the mixture, and carrying out a polymerization reaction under nitrogen protection. After cooling, a neutralizing agent is added for a neutralization reaction. Then, water is added for dispersion and emulsification. Finally, ethylenediamine is added for a post-chain extension reaction. After filtration, the self-cleaning waterborne polyurethane is obtained.

[0007] The phosphorus-containing diol is P-polyol;

[0008] The fluorinated diol is prepared by the following method:

[0009] Step 1: Polymerize a fluorinated monohydric alcohol and an aliphatic diisocyanate at a molar ratio of 1:1 to 1.2 to obtain an intermediate;

[0010] Step 2: The intermediate is polymerized with diethanolamine to obtain a fluorinated diol, and the molar ratio of diethanolamine to aliphatic diisocyanate in step 1 is 1:1 to 1.2.

[0011] Preferably, step 1 specifically involves: mixing a fluorinated monohydric alcohol, an aliphatic diisocyanate, and a catalyst, and heating the mixture to 60–80°C for 1.5–2 hours to obtain an intermediate;

[0012] The catalyst is selected from at least one of dibutyltin dilaurate and stannous octoate.

[0013] Preferably, step 2 specifically involves reacting the intermediate obtained in step 1 with diethanolamine at -10 to 0°C for 5 to 12 minutes to obtain a fluorinated diol.

[0014] Preferably, the adipic acid-based polyester polyol is selected from any one of polytetrahydrofuran, polypropylene glycol, polyethylene glycol, and polycaprolactone;

[0015] The aliphatic diisocyanate is selected from any one of isophorone diisocyanate, hexamethylene diisocyanate, and lysine diisocyanate;

[0016] The pre-chain extender solution is selected from any one of 2,2-dimethylolpropionic acid solution, dimethylolbutyric acid solution, sodium ethylenediamine ethanesulfonate solution, N-methyldiethanolamine solution, and triethanolamine solution.

[0017] Preferably, the mass ratio of the adipic acid-based polyester polyol, aliphatic diisocyanate, fluorinated diol, phosphorus-containing diol P-polyol, pre-chain extender solution, neutralizer, and ethylenediamine is 2.2–3.7: 5.0–8.3: 0.9–1.5: 0.1–0.4: 5.6–10.0: 0.7–1.4: 0.6–0.8.

[0018] The concentration of the pre-chain extender in the pre-chain extender solution is 0.15–0.3 g / mL.

[0019] Preferably, the preparation method of the self-cleaning waterborne polyurethane is as follows: mixing adipic acid-based polyester polyol, aliphatic diisocyanate, fluorinated diol, phosphorus-containing diol and pre-chain extender solution, heating to 60-80°C, and reacting under nitrogen protection for 2-4 hours;

[0020] The temperature was then lowered to 40–45°C, and a neutralizing agent was added for neutralization. Water was then added for dispersion and emulsification. Ethylenediamine was then added for post-chain extension. After filtration, self-cleaning waterborne polyurethane was obtained.

[0021] Preferably, an inorganic filler is also added, wherein the inorganic filler is selected from at least one of nano-lithium silicate, titanium dioxide, and graphene;

[0022] Furthermore, the mass ratio of inorganic filler to aliphatic diisocyanate is 0.05–0.15: 5.0–8.3.

[0023] Preferably, the preparation method of the self-cleaning waterborne polyurethane is as follows: mixing adipic acid-based polyester polyol, inorganic filler, aliphatic diisocyanate, fluorinated diol, phosphorus-containing diol and pre-chain extender solution, heating to 60-80°C, and reacting under nitrogen protection for 2-4 hours;

[0024] The temperature was then lowered to 40–45°C, and a neutralizing agent was added for neutralization. Water was then added for dispersion and emulsification. Ethylenediamine was then added for post-chain extension. After filtration, self-cleaning waterborne polyurethane was obtained.

[0025] In addition, this application also discloses a self-cleaning waterborne polyurethane, which is prepared by the above-described method for preparing self-cleaning waterborne polyurethane.

[0026] In addition, this application also discloses the application of the self-cleaning waterborne polyurethane as described above in coatings.

[0027] The beneficial effects of this application are:

[0028] The method for preparing waterborne polyurethane with self-cleaning ability provided in this application involves preparing polyurethane using fluorinated diols. Since fluorine is the most electronegative element, the carbon-fluorine bond (CF) has high bond energy and the molecular chains are tightly arranged, forming a low surface energy surface that makes it difficult for water molecules to wet. In addition, fluorine gives polyurethane stronger resistance to acids, alkalis and solvents, preventing the surface from losing its hydrophobicity due to corrosion failure. Detailed Implementation

[0029] The present invention will now be clearly and completely described in conjunction with embodiments thereof. It should be noted that, unless specific conditions are specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0030] Pentafluorobutanol, CAS number 54949-74-5;

[0031] Isophorone diisocyanate, CAS number 4098-71-9;

[0032] Lysine diisocyanate, CAS number 45172-15-4;

[0033] The phosphorus-containing diol P-polyol was purchased from Kaifeng Huashun Chemical Technology Development Co., Ltd.

[0034] Dimethylolbutyric acid, CAS number 10097-02-6

[0035] 2,2-Dimethylolpropionic acid, CAS number 4767-03-7;

[0036] Polytetrahydrofuran was purchased from Guangdong Yuanfeng Chemical Reagent Co., Ltd., with a molecular weight of 600-700.

[0037] Polypropylene glycol was purchased from Haian Petrochemical Plant in Jiangsu Province, with a molecular weight of 700±50.

[0038] Example 1

[0039] Preparation of fluorinated diols:

[0040] Step 1: Mix pentafluorobutanol and acetone and heat to 70°C. Then add isophorone diisocyanate and stannous octoate and stir for 10 min. Then maintain the temperature at 70°C and react for 1.8 h to obtain the intermediate.

[0041] Furthermore, in step 1, the molar ratio of pentafluorobutanol to isophorone diisocyanate is 1:1.1, the mass ratio of acetone to pentafluorobutanol is 5:1, and the mass ratio of stannous octoate to pentafluorobutanol is 1:20.

[0042] Step 2: Cool the intermediate obtained in Step 1 to -6℃, then add diethanolamine to the intermediate and react for 20 min. Then evaporate acetone at 50℃ and 0.09 MPa vacuum to obtain a fluorinated diol. In Step 2, the molar ratio of diethanolamine to aliphatic diisocyanate in Step 1 is 1:1.1.

[0043] Preparation of self-cleaning waterborne polyurethane

[0044] 2.2 g of polytetrahydrofuran, 5.3 g of isophorone diisocyanate, 0.9 g of fluorinated diol, 0.1 g of phosphorus-containing diol P-polyol, and 5.6 g of 2,2-dimethylolpropionic acid solution (concentration 0.2 g / mL) were added to a 500 mL three-necked flask and heated to 60 °C. The mixture was stirred under nitrogen protection for 2 hours to carry out the polymerization reaction. After the reaction was completed, the system temperature was lowered to 40 °C, and 0.8 g of triethylamine was added for neutralization reaction for 30 minutes. Then, deionized water was added and the mixture was stirred at high speed until the emulsion was uniform. Finally, 0.6 g of ethylenediamine was added for post-chain extension reaction for 45 minutes. After the reaction was completed, the mixture was filtered through a 400-mesh nylon screen to obtain a self-cleaning waterborne polyurethane.

[0045] Example 2

[0046] Preparation of fluorinated diols:

[0047] Step 1: Mix pentafluorobutanol and acetone and heat to 60°C. Then add isophorone diisocyanate and stannous octoate and stir for 10 min. Then maintain the temperature at 60°C and react for 1.5 h to obtain the intermediate.

[0048] Furthermore, in step 1, the molar ratio of pentafluorobutanol to isophorone diisocyanate is 1:1.03, the mass ratio of acetone to pentafluorobutanol is 5:1, and the mass ratio of stannous octoate to pentafluorobutanol is 1:20.

[0049] Step 2: Cool the intermediate obtained in Step 1 to -10℃, then add diethanolamine to the intermediate and react for 20 min. Then evaporate acetone at 50℃ and 0.09 MPa vacuum to obtain a fluorinated diol. In Step 2, the molar ratio of diethanolamine to aliphatic diisocyanate in Step 1 is 1:1.2.

[0050] Preparation of self-cleaning waterborne polyurethane

[0051] 3.7 g of polypropylene glycol, 8.3 g of isophorone diisocyanate, 1.5 g of fluorinated diol, 0.4 g of phosphorus-containing diol P-polyol, and 10.0 g of 2,2-dimethylolpropionic acid solution (concentration 0.2 g / mL) were added to a 500 mL three-necked flask. The mixture was heated to 80 °C and stirred under nitrogen protection for 4 hours to carry out the polymerization reaction. After the reaction was completed, the system temperature was lowered to 45 °C, and 0.7 g of triethylamine was added for neutralization reaction for 30 minutes. Then, deionized water was added and the mixture was stirred at high speed until the emulsion was uniform. Finally, 0.8 g of ethylenediamine was added for post-chain extension reaction for 45 minutes. After the reaction was completed, the mixture was filtered through a 400-mesh nylon screen to obtain a self-cleaning waterborne polyurethane.

[0052] Example 3

[0053] Preparation of fluorinated diols:

[0054] Step 1: Mix pentafluorobutanol and acetone and heat to 80°C. Then add isophorone diisocyanate and stannous octoate and stir for 10 min. Then maintain the temperature at 80°C and react for 2 h to obtain the intermediate.

[0055] Furthermore, in step 1, the molar ratio of pentafluorobutanol to isophorone diisocyanate is 1:1.2, the mass ratio of acetone to pentafluorobutanol is 5:1, and the mass ratio of stannous octoate to pentafluorobutanol is 1:20.

[0056] Step 2: Cool the intermediate obtained in Step 1 to 0°C, then add diethanolamine to the intermediate and react for 20 min. Then evaporate acetone at 50°C and 0.09 MPa vacuum to obtain a fluorinated diol. In Step 2, the molar ratio of diethanolamine to aliphatic diisocyanate in Step 1 is 1:1.03.

[0057] Preparation of self-cleaning waterborne polyurethane

[0058] 2.5 g of polytetrahydrofuran, 6.8 g of lysine diisocyanate, 1.3 g of fluorinated diol, 0.3 g of phosphorus-containing diol P-polyol, and 8.2 g of dimethylolbutyric acid solution (concentration 0.2 g / mL) were added to a 500 mL three-necked flask and heated to 70 °C. The mixture was stirred under nitrogen protection for 3 hours to carry out the polymerization reaction. After the reaction was completed, the system temperature was lowered to 40 °C, and 0.8 g of triethylamine was added for neutralization reaction for 30 minutes. Then, deionized water was added and the mixture was stirred at high speed until the emulsion was uniform. Finally, 0.7 g of ethylenediamine was added for post-chain extension reaction for 45 minutes. After the reaction was completed, the mixture was filtered through a 400-mesh nylon screen to obtain a self-cleaning waterborne polyurethane.

[0059] Example 4

[0060] The process is basically the same as in Example 1, except that the preparation of the self-cleaning waterborne polyurethane is different.

[0061] 2.2 g of polytetrahydrofuran, 0.1 g of nano-lithium silicate, 5.3 g of isophorone diisocyanate, 0.9 g of fluorinated diol, 0.1 g of phosphorus-containing diol P-polyol, and 5.6 g of 2,2-dimethylolpropionic acid solution (concentration 0.2 g / mL) were added to a 500 mL three-necked flask. The mixture was heated to 60 °C and stirred under nitrogen protection for 2 hours to carry out the polymerization reaction. After the reaction was completed, the system temperature was lowered to 40 °C, and 0.8 g of triethylamine was added for neutralization reaction for 30 minutes. Then, deionized water was added and the mixture was stirred at high speed until the emulsion was uniform. Finally, 0.6 g of ethylenediamine was added for post-chain extension reaction for 45 minutes. After the reaction was completed, the mixture was filtered through a 400-mesh nylon screen to obtain a self-cleaning waterborne polyurethane.

[0062] Example 5

[0063] The process is basically the same as in Example 1, except that graphene is used instead of nano-lithium silicate in the preparation of self-cleaning waterborne polyurethane.

[0064] Example 6

[0065] The process is basically the same as in Example 1, except that in the preparation of the self-cleaning waterborne polyurethane, a mixture of graphene and nano-lithium silicate is used to replace the nano-lithium silicate, and the mass ratio of graphene to nano-lithium silicate is 1:1.

[0066] Comparative Example 1

[0067] The method is basically the same as in Example 1, except that the preparation method of the self-cleaning waterborne polyurethane is as follows:

[0068] 2.2 g of polytetrahydrofuran, 5.3 g of isophorone diisocyanate, 1.0 g of fluorinated diol, and 5.6 g of 2,2-dimethylolpropionic acid solution (concentration 0.2 g / mL) were added to a 500 mL three-necked flask and heated to 60 °C. The mixture was stirred under nitrogen protection for 2 hours to carry out the polymerization reaction. After the reaction was completed, the system temperature was lowered to 40 °C, and 0.8 g of triethylamine was added for neutralization reaction for 30 minutes. Then, deionized water was added and the mixture was stirred at high speed until the emulsion was uniform. Finally, 0.6 g of ethylenediamine was added for post-chain extension reaction for 45 minutes. After the reaction was completed, the mixture was filtered through a 400-mesh nylon screen to obtain a self-cleaning waterborne polyurethane.

[0069] Comparative Example 2

[0070] The method is basically the same as in Example 1, except that the preparation method of the self-cleaning waterborne polyurethane is as follows:

[0071] 2.2 g of polytetrahydrofuran, 5.3 g of isophorone diisocyanate, 1.0 g of phosphorus-containing diol P-polyol, and 5.6 g of 2,2-dimethylolpropionic acid solution (concentration 0.2 g / mL) were added to a 500 mL three-necked flask and heated to 60 °C. The polymerization reaction was carried out under nitrogen protection with stirring for 2 hours. After the reaction was completed, the system temperature was lowered to 40 °C, and 0.8 g of triethylamine was added for neutralization reaction for 30 minutes. Then, deionized water was added and the mixture was stirred at high speed until the emulsion was uniform. Finally, 0.6 g of ethylenediamine was added for post-chain extension reaction for 45 minutes. After the reaction was completed, the mixture was filtered through a 400-mesh nylon screen to obtain self-cleaning waterborne polyurethane.

[0072] Performance testing

[0073] The polyurethanes prepared in Examples 1-6 and Comparative Examples 1-2 were applied to coatings, and the hydrophobicity and flame retardant properties of the resulting coatings were investigated. The specific test procedures and steps are as follows:

[0074] (1) The coating was prepared into a film on tinplate. After the film dried, the hydrophobicity of the sample surface was evaluated using a static water contact angle meter (SDC-100). 2 μL of deionized water was dropped onto the sample surface, and the static contact angle formed by the droplet on the coating surface was measured. The experiment was repeated 5 times, and the average value was taken.

[0075] (2) The coating was poured into a self-made mold and tested using a CZF-4 horizontal and vertical burner. The sample size was 250×20×20 mm. 3 Specifically, it shall be implemented in accordance with GB / T 8333-2008.

[0076] (3) Pour the coating into a self-made mold and test it using a JF-3 limiting oxygen index meter. The sample size is 80×10×10 mm. 3 The specific procedures should be performed according to GB / T 2406-1993. The experiment was repeated 5 times, and the average value was taken as the test result.

[0077] The test results are shown in Table 1:

[0078] Table 1

[0079] Group Contact angle (°) UL-94 With or without droplets Limiting oxygen index Example 1 116.3 V-0 none 24.1 Example 2 117.8 V-0 none 25.5 Example 3 117.1 V-0 none 24.9 Example 4 118.0 V-0 none 24.7 Example 5 118.7 V-0 none 25.0 Example 6 120.6 V-0 none 24.8 Comparative Example 1 116.6 V-2 have 20.8 Comparative Example 2 108.8 V-2 have 20.3

[0080] Results analysis:

[0081] 1. As can be seen from Examples 1-3, when the amount of raw materials added and the process parameters in the preparation process of self-cleaning waterborne polyurethane in Examples 1-3 are slightly adjusted, the hydrophobicity and flame retardant properties of the waterborne polyurethane prepared in Examples 1-3 fluctuate. Furthermore, as can be seen from Examples 1-3, with the increase of the amount of fluorinated diol, the hydrophobicity of the self-cleaning waterborne polyurethane shows a certain increasing trend.

[0082] 2. Further observation of Examples 1 and 4-6 shows that with the use of inorganic fillers in waterborne polyurethane, the contact angle of waterborne polyurethane is higher than that of Example 1. This indicates that the hydrophobicity of Examples 4-6 is improved compared to Example 1. Furthermore, observation of Example 6 shows that it uses a mixed inorganic filler of graphene and nano-lithium silicate. Compared with Examples 4 and 5 which use nano-lithium silicate and graphene alone, the contact angle of Example 6 is further increased, and its hydrophobicity is further enhanced. It can be seen that using a mixed inorganic filler of the two can further improve the hydrophobicity of waterborne polyurethane. In addition, the flame retardant ability of Examples 4-6 also shows a certain degree of improvement.

[0083] 3. As can be seen from Example 1 and Comparative Examples 1-2, when waterborne polyurethane is modified only by fluorine, its hydrophobicity does not show a significant change compared to Example 1, but its flame retardancy decreases significantly. When only phosphorus is modified, its hydrophobicity decreases significantly. This indicates that the improvement in the hydrophobicity of polyurethane is more due to the use of fluorinated diols. Further observation of flame retardant performance, taking the limiting oxygen index (LOI) as an example, shows that the LIO of Comparative Example 1 is 20.8, and the LIO of Comparative Example 2 is 20.3, while the LIO of Example 1, modified by both fluorine and phosphorus, reaches 24.1. This shows that the co-modification of fluorine and phosphorus improves the flame retardancy of waterborne polyurethane, and the co-modification produces a synergistic effect. This is because, when using fluorine or phosphorus alone, the highest LIO of polyurethane is only 20.8, while with co-modification, the LIO of Example 1 should be between that of Comparative Examples 1-2, but its LIO far exceeds either of them. The reason for this phenomenon may be... Phosphorus can catalyze dehydration, dehydrogenation, and cyclization reactions in the polymer matrix during the initial stage of combustion or thermal decomposition, promoting the formation of carbon-rich, highly cross-linked char residues. Meanwhile, CF bonds are relatively stable at high temperatures, resulting in a fluorinated carbon layer with higher thermal stability and mechanical strength, which is not easily damaged by flames or heat flow, and can more effectively provide thermal and oxygen insulation. When the two work together, phosphorus efficiently catalyzes the polymer to form carbon, while fluorine significantly improves the density, strength, and thermal stability of the formed carbon layer, thereby synergistically enhancing the flame retardant ability of waterborne polyurethane.

[0084] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a self-cleaning waterborne polyurethane, characterized in that, The self-cleaning waterborne polyurethane is prepared by mixing a polyol, a fluorinated diol, an aliphatic diisocyanate, a phosphorus-containing diol, and a pre-chain extender solution, heating the mixture, and performing a polymerization reaction under nitrogen protection; after cooling, a neutralizing agent is added for a neutralization reaction; then water is added for dispersion and emulsification; finally, ethylenediamine is added for a post-chain extension reaction, and after filtration, the self-cleaning waterborne polyurethane is obtained. The phosphorus-containing diol is P-polyol; The fluorinated diol is prepared by the following method: Step 1: Polymerize a fluorinated monohydric alcohol and an aliphatic diisocyanate at a molar ratio of 1:1 to 1.2 to obtain an intermediate; Step 2: The intermediate is polymerized with diethanolamine to obtain a fluorinated diol, and the molar ratio of diethanolamine to aliphatic diisocyanate in step 1 is 1:1 to 1.2; The mass ratio of the polyol, aliphatic diisocyanate, fluorinated diol, phosphorus-containing diol P-polyol, pre-chain extender solution, neutralizer and ethylenediamine is 2.2-3.7: 5.0-8.3: 0.9-1.5: 0.1-0.4: 5.6-10.0: 0.7-1.4: 0.6-0.8; In the pre-chain extender solution, the concentration of the pre-chain extender is 0.15–0.3 g / mL; Inorganic fillers are also added, namely graphene and nano-lithium silicate, and the mass ratio of graphene to nano-lithium silicate is 1:

1. The mass ratio of the inorganic filler to the aliphatic diisocyanate is 0.05–0.15: 5.0–8.3; The polyol is selected from any one of polytetrahydrofuran, polypropylene glycol, polyethylene glycol, and polycaprolactone.

2. The method for preparing self-cleaning waterborne polyurethane according to claim 1, characterized in that, Step 1 specifically involves mixing a fluorinated monohydric alcohol, an aliphatic diisocyanate, and a catalyst, and heating the mixture to 60–80°C for 1.5–2 hours to obtain an intermediate. The catalyst is selected from at least one of dibutyltin dilaurate and stannous octoate.

3. The method for preparing self-cleaning waterborne polyurethane according to claim 1, characterized in that, Step 2 specifically involves reacting the intermediate obtained in step 1 with diethanolamine at -10 to 0°C for 5 to 12 minutes to obtain a fluorinated diol.

4. The method for preparing self-cleaning waterborne polyurethane according to claim 1, characterized in that, The aliphatic diisocyanate is selected from any one of isophorone diisocyanate, hexamethylene diisocyanate, and lysine diisocyanate; The pre-chain extender solution is selected from any one of 2,2-dimethylolpropionic acid solution, dimethylolbutyric acid solution, sodium ethylenediamine ethanesulfonate solution, and N-methyldiethanolamine solution.

5. The method for preparing self-cleaning waterborne polyurethane according to claim 1, characterized in that, The preparation method of the self-cleaning waterborne polyurethane is as follows: a polyol, inorganic filler, aliphatic diisocyanate, fluorinated diol, phosphorus-containing diol and pre-chain extender solution are mixed, heated to 60-80°C, and reacted for 2-4 hours under nitrogen protection. The temperature was then lowered to 40–45°C, and a neutralizing agent was added for neutralization. Water was then added for dispersion and emulsification. Ethylenediamine was then added for post-chain extension. After filtration, self-cleaning waterborne polyurethane was obtained.

6. A self-cleaning waterborne polyurethane, characterized in that, It is prepared by the method described in any one of claims 1-5 for the preparation of self-cleaning waterborne polyurethane.

7. The application of the self-cleaning waterborne polyurethane as described in claim 6 in coatings.