PU water-based polyurethane weather-resistant waterproof material and preparation method thereof

Abstract

The application relates to the technical field of waterproof materials, in particular to a PU water-based polyurethane weather-resistant waterproof material and a preparation method thereof, which contains the following raw materials in parts by weight: water-based polyurethane emulsion 60-85 parts, modified nano-silicon dioxide agent 3-10 parts, weather-resistant agent 2-8 parts, film-forming aid 2-6 parts, defoaming agent 0.3-1.5 parts, wet dispersing agent 0.5-2 parts, thickening agent 0.5-2 parts and water 5-15 parts. The mechanical property and water resistance of the waterproof material are remarkably improved by adding the modified nano-silicon dioxide agent; the surface of the nano-silicon dioxide is grafted and modified by a silane coupling agent KH-550, the dispersibility of the nano particles in the polyurethane matrix and the interface compatibility with the matrix are improved, the mechanical strength and crack resistance of the coating are further improved by taking carbon nanotubes as reinforcing fillers, and the hardness and wear resistance of the coating are improved by taking nano-aluminum oxide.

Description

Technical Field

[0001] This invention relates to the field of waterproof materials technology, specifically to a waterborne polyurethane weather-resistant waterproof material and its preparation method. Background Technology

[0002] Polyurethane waterproof coatings are widely used in the field of building waterproofing due to their excellent elasticity, weather resistance and waterproof performance. With increasingly stringent environmental regulations, water-based polyurethane waterproof materials, which use water as a dispersion medium, have advantages such as low VOC emissions, safe construction and good adhesion to the substrate. They are gradually replacing traditional solvent-based polyurethane waterproof materials. Water-based polyurethane molecular chains contain polar groups such as urethane bonds, ester bonds, ether bonds and amide bonds. These groups endow the material with excellent adhesion, flexibility and corrosion resistance, but also lead to the need to improve its water resistance, heat resistance and mechanical properties.

[0003] However, waterborne polyurethane waterproofing materials still face many technical challenges in practical applications. First, the molecular chains of waterborne polyurethane contain hydrophilic groups, which can easily cause the coating to swell or even peel off under long-term immersion in water, resulting in insufficient waterproofing durability. Second, polyurethane materials are prone to photo-oxidative aging reactions under ultraviolet light, and the molecular chains break down, leading to powdering, cracking, and loss of gloss in the coating, thus shortening its service life. Studies have shown that introducing nano-silica into waterborne polyurethane can significantly improve the water resistance, thermal stability, and mechanical properties of the coating. Surface modification of nano-silica with silane coupling agents can improve the dispersion of nanoparticles in the polymer matrix and the interfacial compatibility with the matrix. In addition, hindered amine light stabilizers have the function of capturing free radicals generated by ultraviolet light, which can effectively inhibit the loss of gloss, cracking, blistering, and discoloration of the coating.

[0004] In the prior art, some solutions use nano-silica to modify waterborne polyurethane to improve mechanical properties, and some solutions add light stabilizers to improve weather resistance. However, the systematic compounding of modified nano-silica with weathering agents to synergistically improve the mechanical properties, water resistance and weather durability of waterproof materials has not been fully disclosed. Based on this, the present invention provides a PU waterborne polyurethane weather-resistant waterproof material and its preparation method. Summary of the Invention

[0005] In view of the deficiencies of the prior art, the purpose of this invention is to provide a waterborne polyurethane weather-resistant and waterproof material and its preparation method, so as to solve the problems mentioned in the background art.

[0006] The present invention solves the technical problem by adopting the following technical solution: This invention provides a water-based polyurethane weather-resistant and waterproof material, comprising the following raw materials by weight: The ingredients are: 60-85 parts of waterborne polyurethane emulsion, 3-10 parts of modified nano silica agent, 2-8 parts of weathering agent, 2-6 parts of film-forming aid, 0.3-1.5 parts of defoamer, 0.5-2 parts of wetting and dispersing agent, 0.5-2 parts of thickener, and 5-15 parts of water.

[0007] The modified nano silica agent is prepared by the following steps: preheating nano silica at 55-60℃ for 1 hour to obtain preheated nano silica; mixing the preheated nano silica and the modification liquid at a weight ratio of 3:5-7 for modification treatment; stirring at a speed of 350-450 r / min for 1 hour; after stirring, filtering and drying to obtain the modified nano silica agent.

[0008] Preferably, the waterborne polyurethane emulsion is an anionic aliphatic waterborne polyurethane emulsion with a solid content of 35%-50%. Aliphatic waterborne polyurethane has better yellowing resistance than aromatic polyurethane, making it suitable for outdoor weather-resistant applications.

[0009] Preferably, the modified liquid is prepared by the following steps: S1: Mix 3-5 parts of silane coupling agent KH-550, 1-3 parts of chitosan solution with a mass fraction of 2%-5%, and 10-15 parts of ethanol solution with a mass fraction of 75%-85% evenly to obtain silane solution. S2: Add 2-5 parts of carbon nanotubes and 1-3 parts of nano-alumina to 5-8 parts of silane solution and mix evenly to obtain the modified solution.

[0010] Silane coupling agent KH-550 is used to perform surface grafting modification on nano-silica, introducing organic functional groups onto its surface to improve the dispersibility of nanoparticles in the polyurethane matrix and their interfacial compatibility with the matrix. Chitosan provides amino active groups, which can enhance the chemical bonding between nano-silica and polyurethane molecular chains. Carbon nanotubes, as reinforcing fillers, can improve the mechanical strength and crack resistance of the coating. The addition of nano-alumina can improve the hardness and wear resistance of the coating. The synergistic effect of the components gives the modified nano-silica agent good dispersibility and functional enhancement effect.

[0011] Preferably, the weathering agent comprises, by weight, 40-60 parts of hindered amine light stabilizer, 25-40 parts of ultraviolet absorber, and 5-15 parts of antioxidant.

[0012] Preferably, the hindered amine light stabilizer is bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, the ultraviolet absorber is 2-(2′-hydroxy-3′,5′-di-tert-butylphenyl)-5-chlorobenzotriazole, and the antioxidant is antioxidant 1010 or antioxidant 168.

[0013] Hindered amine light stabilizers can capture free radicals generated by ultraviolet light, inhibiting coating gloss loss, cracking and discoloration. Ultraviolet absorbers can absorb harmful ultraviolet light and convert it into harmless heat energy. Antioxidants can inhibit thermo-oxidative aging reactions. When used in combination, these three can produce synergistic anti-aging and anti-yellowing effects, significantly improving the weather resistance of coatings.

[0014] Preferably, the film-forming aid is dipropylene glycol butyl ether or diethylene glycol butyl ether acetate, the defoamer is a polyether-modified polysiloxane defoamer, the wetting and dispersing agent is a sodium polycarboxylate dispersant, and the thickener is a polyurethane associative thickener.

[0015] This invention also provides a method for preparing a waterborne polyurethane weather-resistant and waterproof material, comprising the following steps: S100: Preparation of modified nano silica agent: Preheat nano silica at 55-60℃ for 1h to obtain preheated nano silica. Mix the preheated nano silica and the modification liquid at a weight ratio of 3:5-7 and stir for modification treatment. Stir at a speed of 350-450r / min for 1h. After stirring, filter and dry to obtain modified nano silica agent. S200: Pre-dispersion of weathering agent: Hindered amine light stabilizer, ultraviolet absorber and antioxidant are mixed in proportion, and an appropriate amount of film-forming aid is added. The mixture is stirred at 40-60℃ to dissolve and disperse evenly to obtain a pre-dispersion of weathering agent. S300: Preparation of waterborne polyurethane base material: Add waterborne polyurethane emulsion to the reactor, and add modified nano silica agent, weather-resistant pre-dispersion liquid, wetting and dispersing agent and part of water in sequence under stirring conditions, and stir and disperse at 500-800r / min for 15-30min. S400: Additives and paint mixing: Add defoamer, thickener and remaining film-forming aid to the system obtained in step S300, adjust the pH to 7.5-8.5, add the remaining water, and stir at 300-500 r / min for 10-20 min to obtain PU waterborne polyurethane weather-resistant waterproof material.

[0016] Preferably, in step S200, the temperature for stirring, dissolving, and dispersing is 45-55°C, and the stirring time is 20-40 min.

[0017] Preferably, in step S300, the stirring speed is 600-700 r / min and the stirring time is 20-25 min.

[0018] The present invention also provides an application of a waterborne polyurethane weather-resistant waterproof material. The waterproof material is applied by brushing, rolling or spraying, with a coating amount of 1.5-3.0 kg / m², and is cured naturally for 7-14 days. It is used for waterproofing and protection of building roofs, underground projects, bridges and tunnels or water conservancy projects.

[0019] Compared with the prior art, the present invention has the following beneficial effects: First, the present invention significantly improves the mechanical properties and water resistance of waterproof materials by adding modified nano-silica agent. Silane coupling agent KH-550 performs surface grafting modification on nano-silica, improving the dispersion of nanoparticles in the polyurethane matrix and their interfacial compatibility with the matrix. Carbon nanotubes, as reinforcing fillers, further enhance the mechanical strength and crack resistance of the coating. Nano-alumina improves the hardness and wear resistance of the coating.

[0020] Secondly, by adding weathering agents in combination, this invention significantly enhances the UV aging resistance of waterproof materials. The hindered amine light stabilizer and UV absorber work synergistically to prevent coating loss of gloss, cracking, blistering, peeling and discoloration. The hindered amine light stabilizer has the function of capturing free radicals generated by UV light, which can effectively inhibit coating aging. The combination of the three can produce synergistic anti-aging and anti-yellowing effects, significantly extending the service life of the material.

[0021] Third, this invention achieves simultaneous improvement in the mechanical properties and weather resistance of waterproof materials through the synergistic combination of modified nano-silica agent and weather-resistant agent. The modified nano-silica agent constructs a dense physical cross-linking network, which improves the density and waterproofness of the coating. The weather-resistant agent captures free radicals and absorbs ultraviolet light at the molecular level, which delays the aging and degradation of the material. The synergistic effect of the two enables the waterproof material to maintain excellent waterproof effect and mechanical properties during long-term outdoor use.

[0022] Fourth, the preparation method of this invention is simple to operate, the components have good compatibility, high storage stability, and strong construction adaptability. It is applicable to various waterproofing and protection scenarios such as building roofs, underground engineering, bridges and tunnels, and water conservancy projects, and has good prospects for promotion and application. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to specific examples. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Example 1 A waterborne polyurethane weather-resistant and waterproof material comprises the following raw materials by weight: 75 parts waterborne polyurethane emulsion, 6 parts modified nano silica agent, 5 parts weather-resistant agent, 4 parts dipropylene glycol butyl ether, 0.8 parts polyether modified polysiloxane defoamer, 1 part sodium polycarboxylate dispersant, 1 part polyurethane associative thickener, and 10 parts water.

[0025] Preparation of modified nano silica agent: Nano silica was preheated at 58℃ for 1 h to obtain preheated nano silica. The preheated nano silica and the modification liquid were stirred and modified at a weight ratio of 3:6. The stirring speed was 400 r / min and the stirring was carried out for 1 h. After stirring was completed, the mixture was filtered and dried to obtain the modified nano silica agent.

[0026] Preparation of modified solution: Mix 4 parts of silane coupling agent KH-550, 2 parts of chitosan solution with a mass fraction of 3% and 12 parts of ethanol solution with a mass fraction of 80% to obtain silane solution; add 3 parts of carbon nanotubes and 2 parts of nano alumina to 6 parts of silane solution and mix to obtain modified solution.

[0027] The weathering agent comprises, by weight, 50 parts of hindered amine light stabilizer (bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, 35 parts of ultraviolet absorber (2-(2′-hydroxy-3′,5′-di-tert-butylphenyl)-5-chlorobenzotriazole), and 15 parts of antioxidant 1010.

[0028] Preparation method: S100: Modified nano-silica agent prepared according to the above method; S200: Mix hindered amine light stabilizer, ultraviolet absorber and antioxidant according to the ratio, add 2 parts of dipropylene glycol butyl ether, stir at 50℃ to dissolve and disperse for 30 min to obtain weathering agent predispersant; S300: Add the waterborne polyurethane emulsion to the reactor, and under stirring conditions, add the modified nano silica agent, weather-resistant pre-dispersion liquid, sodium polycarboxylate dispersant and 8 parts of water in sequence, and stir and disperse at 650 r / min for 20 min. S400: Add polyether-modified polysiloxane defoamer, polyurethane associative thickener and 2 parts of the remaining dipropylene glycol butyl ether to the system obtained in step S300, adjust the pH to 8.0, add 2 parts of the remaining water, and stir at 400 r / min for 15 min to obtain PU waterborne polyurethane weather-resistant waterproof material.

[0029] Example 2 A waterborne polyurethane weather-resistant and waterproof material, which differs from Example 1 in that it contains 65 parts waterborne polyurethane emulsion, 4 parts modified nano silica agent, 3 parts weather-resistant agent, 3 parts dipropylene glycol butyl ether, 0.5 parts defoamer, 0.8 parts wetting and dispersing agent, 0.8 parts thickener, and 8 parts water.

[0030] In the preparation of the modified nano-silica agent, the preheating temperature was 55℃, the weight ratio of nano-silica to the modifying liquid was 3:5, and the stirring speed was 350 r / min. The modifying liquid consisted of 3 parts KH-550, 1 part chitosan solution, 10 parts ethanol solution, 2 parts carbon nanotubes, 1 part nano-alumina, and 5 parts silane solution. The weathering agent contained 40 parts hindered amine light stabilizer, 25 parts ultraviolet absorber, and 10 parts antioxidant 168.

[0031] The preparation method is the same as in Example 1. In step S200, the stirring temperature is 45°C and the stirring time is 25 min; in step S300, the stirring speed is 600 r / min and the stirring time is 18 min.

[0032] Example 3 A waterborne polyurethane weather-resistant and waterproof material, which differs from Example 1 in that it contains 80 parts of waterborne polyurethane emulsion, 8 parts of modified nano silica agent, 7 parts of weather-resistant agent, 5 parts of diethylene glycol butyl ether acetate, 1.2 parts of defoamer, 1.5 parts of wetting and dispersing agent, 1.5 parts of thickener, and 12 parts of water.

[0033] In the preparation of the modified nano-silica agent, the preheating temperature was 60℃, the weight ratio of nano-silica to the modifying liquid was 3:7, and the stirring speed was 450 r / min. The modifying liquid consisted of 5 parts KH-550, 3 parts chitosan solution, 15 parts ethanol solution, 5 parts carbon nanotubes, 3 parts nano-alumina, and 8 parts silane solution. The weathering agent contained 55 parts hindered amine light stabilizer, 38 parts ultraviolet absorber, and 15 parts antioxidant 1010.

[0034] The preparation method is the same as in Example 1. In step S200, the stirring temperature is 55°C and the stirring time is 40 min; in step S300, the stirring speed is 750 r / min and the stirring time is 25 min.

[0035] Scale settings To verify the synergistic effect of the modified nano-silica agent and weather-resistant agent of the present invention, the following 6 comparative examples were set up based on Example 1: Comparative Example 1: No modified nano-silica agent was added (replaced with an equal amount of unmodified nano-silica), and the rest was the same as in Example 1.

[0036] Comparative Example 2: No weathering agent was added, and the rest was the same as in Example 1.

[0037] Comparative Example 3: In the preparation of the modified nano silica agent, the silane coupling agent KH-550 was not added to the modified liquid (it was replaced with an equal amount of deionized water), and the rest was the same as in Example 1.

[0038] Comparative Example 4: In the preparation of the modified nano silica agent, carbon nanotubes were not added to the modified liquid (the same amount of nano silica was used instead), and the rest was the same as in Example 1.

[0039] Comparative Example 5: The weathering agent does not contain hindered amine light stabilizers (only contains UV absorbers and antioxidants), and the rest is the same as in Example 1.

[0040] Comparative Example 6: The weathering agent does not contain any ultraviolet absorbers (only hindered amine light stabilizers and antioxidants), and is otherwise the same as in Example 1.

[0041] Performance testing Performance tests were conducted on the waterborne polyurethane weather-resistant and waterproof materials prepared in Examples 1 to 3 and Comparative Examples 1 to 6: 1. Mechanical property testing The tensile strength and elongation at break were tested according to GB / T 16777-2008 "Test Methods for Waterproof Coatings for Buildings". The results are shown in Table 1. Table 1 Mechanical properties of each embodiment and comparative example

[0042] 2. Water resistance test The water absorption rate and appearance changes of the coating film after immersion in water for 168 hours were tested according to GB / T 16777-2008. The results are shown in Table 2: Table 2 Water resistance performance of each embodiment and comparative example

[0043] 3. Weather resistance test Artificial accelerated aging tests were conducted according to GB / T 14522-2008 (QUV-B, 313nm lamp, 4h illumination / 4h condensation cycle, 72℃ / 50℃). The gloss retention rate was tested after 168h, 336h, and 504h, and the results are shown in Table 3. Table 3 Weather resistance (gloss retention) of each embodiment and comparative example

[0044] 4. Adhesion Test The adhesion between the coating and the cement substrate was tested using the pull-off method according to GB / T 5210-2006. The results are shown in Table 4. Table 4 Adhesion strength of each embodiment and comparative example

[0045] Results analysis: In terms of mechanical properties, the tensile strength of Examples 1-3 reached 4.2-5.2 MPa, and the elongation at break reached 385%-450%, which was significantly better than that of Comparative Example 1. Comparative Example 1 used unmodified nano-silica, and the nanoparticles had poor dispersion in the matrix, resulting in a significant decrease in mechanical properties. This indicates that the surface modification and functional enhancement of the modified nano-silica agent are crucial to improving mechanical properties. Comparative Example 3 had no KH-550 modification, and Comparative Example 4 had no carbon nanotube reinforcement. The tensile strength of both examples was lower than that of the examples, indicating that silane coupling agent modification and carbon nanotube reinforcement both play an important role in improving mechanical properties.

[0046] Regarding water resistance, the water absorption rates of Examples 1 to 3 after 168 hours were 4.5%-6.8%, which were significantly better than those of Comparative Example 1. The modified nano silica agent formed a dense physical cross-linked network in the polyurethane matrix, which effectively blocked the penetration of water molecules. The water absorption rates of Comparative Example 3 and Comparative Example 4 were 7.5% and 7.2%, respectively, which were higher than those of Examples 1 and 2, further verifying the synergistic effect of each component of the modified liquid on improving water resistance.

[0047] Regarding weather resistance, the gloss retention rates of Examples 1-3 after 504 hours of accelerated artificial aging still reached 75.2%-81.5%, which was significantly better than that of Comparative Example 2. Comparative Example 2 did not add weathering agent, and its gloss retention rate dropped sharply, indicating that weathering agent is crucial for resisting ultraviolet aging. The gloss retention rates of Comparative Example 5 and Comparative Example 6 after 504 hours were 60.8% and 58.5%, respectively, both lower than the 78.6% of Example 1, indicating that the combination of hindered amine light stabilizer and ultraviolet absorber has a synergistic anti-aging effect, and neither can be omitted.

[0048] Regarding adhesion, the adhesion of Examples 1 to 3 reached 2.5-3.0 MPa, which is better than that of Comparative Example 1. The active groups on the surface of the modified nano silica agent can form chemical bonds with the polyurethane molecular chains and the substrate surface, thereby improving the interfacial bonding of the coating.

[0049] In summary, the PU waterborne polyurethane weather-resistant waterproof material prepared by the synergistic compounding of modified nano-silica agent and weather-resistant agent exhibits excellent mechanical properties, water resistance, weather resistance, and adhesion. The comparative examples fully verify the necessity of silane coupling agent modification and carbon nanotube reinforcement in the preparation of modified nano-silica agent, as well as the synergistic effect of the compounding of hindered amine light stabilizer and ultraviolet absorber in weather-resistant agent, highlighting the inventiveness and practical value of the present invention.

[0050] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0051] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A waterborne polyurethane weather-resistant and waterproof material, characterized in that, It contains the following ingredients by weight: The ingredients are: 60-85 parts of waterborne polyurethane emulsion, 3-10 parts of modified nano silica agent, 2-8 parts of weathering agent, 2-6 parts of film-forming aid, 0.3-1.5 parts of defoamer, 0.5-2 parts of wetting and dispersing agent, 0.5-2 parts of thickener, and 5-15 parts of water. The modified nano-silica agent is prepared through the following steps: Preheat nano-silica at 55-60℃ for 1 hour to obtain preheated nano-silica. Mix the preheated nano-silica and the modification liquid at a weight ratio of 3:(5-7) and stir for 1 hour at a stirring speed of 350-450 r / min. After stirring, filter and dry to obtain modified nano-silica agent.

2. The PU waterborne polyurethane weather-resistant and waterproof material according to claim 1, characterized in that, The aqueous polyurethane emulsion is an anionic aliphatic aqueous polyurethane emulsion with a solid content of 35%-50%.

3. The PU waterborne polyurethane weather-resistant and waterproof material according to claim 1, characterized in that, The modified liquid is prepared by the following steps: S1: Mix 3-5 parts of silane coupling agent KH-550, 1-3 parts of chitosan solution with a mass fraction of 2%-5%, and 10-15 parts of ethanol solution with a mass fraction of 75%-85% evenly to obtain silane solution. S2: Add 2-5 parts of carbon nanotubes and 1-3 parts of nano-alumina to 5-8 parts of silane solution and mix evenly to obtain the modified solution.

4. The PU waterborne polyurethane weather-resistant and waterproof material according to claim 1, characterized in that, The weathering agent comprises, by weight, 40-60 parts hindered amine light stabilizer, 25-40 parts ultraviolet absorber, and 5-15 parts antioxidant.

5. The PU waterborne polyurethane weather-resistant and waterproof material according to claim 4, characterized in that, The hindered amine light stabilizer is bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, the ultraviolet absorber is 2-(2′-hydroxy-3′,5′-di-tert-butylphenyl)-5-chlorobenzotriazole, and the antioxidant is antioxidant 1010 or antioxidant 168.

6. The PU waterborne polyurethane weather-resistant and waterproof material according to claim 1, characterized in that, The film-forming aid is dipropylene glycol butyl ether or diethylene glycol butyl ether acetate, the defoamer is a polyether-modified polysiloxane defoamer, the wetting and dispersing agent is a sodium polycarboxylate dispersant, and the thickener is a polyurethane associative thickener.

7. A method for preparing a waterborne polyurethane weather-resistant and waterproof material as described in any one of claims 1-6, characterized in that, Includes the following steps: S100: Preparation of modified nano silica agent: Preheat nano silica at 55-60℃ for 1h to obtain preheated nano silica. Mix the preheated nano silica and the modification liquid at a weight ratio of 3:5-7 and stir for modification treatment. Stir at a speed of 350-450r / min for 1h. After stirring, filter and dry to obtain modified nano silica agent. S200: Pre-dispersion of weathering agent: Hindered amine light stabilizer, ultraviolet absorber and antioxidant are mixed in proportion, and an appropriate amount of film-forming aid is added. The mixture is stirred at 40-60℃ to dissolve and disperse evenly to obtain a pre-dispersion of weathering agent. S300: Preparation of waterborne polyurethane base material: Add waterborne polyurethane emulsion to the reactor, and add modified nano silica agent, weather-resistant pre-dispersion liquid, wetting and dispersing agent and part of water in sequence under stirring conditions, and stir and disperse at 500-800r / min for 15-30min. S400: Additives and paint mixing: Add defoamer, thickener and remaining film-forming aid to the system obtained in step S300, adjust the pH to 7.5-8.5, add the remaining water, and stir at 300-500 r / min for 10-20 min to obtain PU waterborne polyurethane weather-resistant waterproof material.

8. The preparation method according to claim 7, characterized in that, In step S200, the temperature for stirring, dissolving, and dispersing is 45-55℃, and the stirring time is 20-40 minutes.

9. The preparation method according to claim 7, characterized in that, In step S300, the stirring speed is 600-700 r / min, and the stirring time is 20-25 min.

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