Self-repairing hydrophobic waterborne polyurethane emulsion and method for preparing the same

Abstract

The application discloses a preparation method of self-repairing hydrophobic water-based polyurethane emulsion, and is characterized by comprising the following steps: (1) preparing an oxime-containing urethane prepolymer A (2) adding polyhydric alcohol and hydroxyl silicone oil into a four-necked flask, heating to 80-120 DEG C, vacuum dewatering for 1 hour, then adding a crosslinking agent, the oxime-containing urethane prepolymer A, 3-7 parts of a carboxyl-containing raw material, continuously adding diisocyanate and a catalyst, heating to 80 DEG C and reacting for 5 hours, finally heating to 100 DEG C and reacting for 1-2 hours; after testing NCO and being qualified, cooling to below 80 DEG C, adding a neutralizing agent and water, then continuously adding water, stirring for 1 hour, and obtaining the self-repairing hydrophobic water-based polyurethane emulsion. The water-based polyurethane emulsion prepared by the method has good hydrophobicity and self-repairing performance, the protection of the water-based polyurethane emulsion on a substrate is more durable, and the maintenance cost is lower.

Description

Technical Field

[0001] This invention relates to the field of waterborne chemical coatings technology, and particularly to a self-healing hydrophobic waterborne polyurethane emulsion and its preparation method. Background Technology

[0002] With the nation's strong advocacy for the use of environmentally friendly materials to reduce pollution and damage, the traditional coatings industry is gradually shifting from oil-based coatings to more environmentally friendly water-based coatings, high-solids coatings, powder coatings, and UV-cured coatings. This reduces organic emissions, and the market environment has spurred the rapid development of the water-based emulsion market. Traditional polyurethane emulsions, due to their excellent elasticity, weather resistance, adhesion, chemical resistance, and superior bonding strength, hold a significant market share. Water-based polyurethane is produced using two methods: forward emulsification and reverse emulsification. Forward emulsification involves adding amine neutralizers or sulfonates to water-liquidize the resin. This method produces emulsions with small particle size and stability, but slightly lower water resistance, making them suitable for long-term storage. Reverse emulsification involves directly adding the resin to a mixture of neutralizer and water at high temperature. This method typically produces emulsions with larger particle size and molecular weight, better water resistance, but poorer storage stability.

[0003] Commercially available polyurethane emulsions generally have poor water resistance and self-healing ability. Many modification methods involve multiple hydrogen bonds or the use of disulfide bonds. Summary of the Invention

[0004] The purpose of this invention is to provide a self-healing hydrophobic aqueous polyurethane emulsion and its preparation method, thereby solving one or more of the problems in the prior art.

[0005] On one hand, the method for preparing the self-healing hydrophobic aqueous polyurethane emulsion provided by the present invention includes the following steps: (1) Preparation of prepolymer A containing oxime ester Add acetone solvent and dioxime raw material, heat to 50-55℃, slowly add diisocyanate, keep warm for 6-10 hours after the addition is completed, and after the NCO test is qualified, remove acetone and discharge the material for later use. (2) Add polyol and hydroxyl silicone oil to a four-necked flask, heat to 80-120℃, dehydrate under vacuum for 1 hour, then add crosslinking agent, oxime urethane prepolymer A, and raw materials containing 3-7 parts of carboxyl groups, continue to add diisocyanate and catalyst, heat to 80℃ and react for 5 hours, and finally heat to 100℃ and react for 1-2 hours; after the NCO test is qualified, cool down to below 80℃, add neutralizing agent and water, then continue to add water, stir for 1 hour, and obtain self-healing hydrophobic waterborne polyurethane emulsion.

[0006] In some embodiments, the preparation method of the self-healing hydrophobic aqueous polyurethane emulsion includes the following steps: (1) Preparation of prepolymer A containing oxime ester Add 2-10 parts of acetone solvent and 3-5 parts of dioxime raw material, heat to 50-55℃, slowly add 5-10 parts of diisocyanate, keep warm for 6-10 hours after the addition is completed, and after the NCO test is qualified, remove acetone and discharge for later use. (2) Add 10-20 parts of polyol and 1-5 parts of hydroxyl silicone oil to a four-necked flask, heat to 80-120℃, dehydrate under vacuum for 1 hour, then add 1-5 parts of crosslinking agent, 5-10 parts of oxime urethane prepolymer A, and 3-7 parts of carboxyl-containing raw materials, then add 5-20 parts of diisocyanate, add 0.1%-1% of catalyst by total mass, heat to 80℃ and react for 5 hours, then heat to 100℃ and react for 1-2 hours; after the NCO test is qualified, cool down to below 80℃, add 3-5 parts of neutralizing agent and mix with 70 parts of water, then add 100-400 parts of water, stir at high speed for 1 hour, and obtain a self-healing hydrophobic waterborne polyurethane emulsion.

[0007] In some embodiments, the dioxime raw material in step (1) is one or a mixture of several of the following: dioxime, dimethyl dioxime, acetylacetone dioxime, and cyclohexanedione dioxime; preferably dimethyl dioxime.

[0008] In some embodiments, the diisocyanate in step (1) is one or more of hexamethylene diisocyanate, toluene diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, and diphenylmethane diisocyanate, preferably isophorone diisocyanate.

[0009] In some embodiments, the polyol mentioned in step (2) is one or a mixture of several polyether polyols, polyester polyols, polycarbonate polyols, and polytetrahydrofuran ester polyols; preferably, polyether polyol 500-1000, polyester polyol 2000, polycarbonate 2000, or polytetrahydrofuran polyol 300-1000.

[0010] In some embodiments, the hydroxyl silicone oil mentioned in step (2) is a hydroxyl silicone oil with a molecular weight of 200-2000.

[0011] In some embodiments, the crosslinking agent in step (2) is one or a mixture of ethylenediamine, diethylenetriamine, triethylenetetramine, trihydroxypropane, glycerol, and pentaerythritol; preferably ethylenediamine or trimethylolpropane.

[0012] In some implementations, the carboxyl-containing raw material in step (2) is one or a mixture of two of dimethylolpropionic acid and dimethylolbutyric acid.

[0013] In some implementations, the catalyst in step (2) is dibutyltin dilaurate.

[0014] In some embodiments, the diisocyanate in step (2) is one or more of hexamethylene diisocyanate, toluene diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, and diphenylmethane diisocyanate, preferably hexamethylene diisocyanate or dicyclohexylmethane diisocyanate.

[0015] In some embodiments, the neutralizing agent in step (2) is one or more of ammonia, triethylamine, dimethylethanolamine, and triethanolamine, preferably triethylamine.

[0016] On the other hand, the self-healing hydrophobic aqueous polyurethane emulsion provided by the present invention is prepared by the following method: (1) Preparation of prepolymer A containing oxime ester Add acetone solvent and dioxime raw material, heat to 50-55℃, slowly add diisocyanate, keep warm for 6-10 hours after the addition is completed, and after the NCO test is qualified, remove acetone and discharge the material for later use. (2) Add polyol and hydroxyl silicone oil to a four-necked flask, heat to 80-120℃, dehydrate under vacuum for 1 hour, then add crosslinking agent, oxime urethane prepolymer A, and raw materials containing 3-7 parts of carboxyl groups, continue to add diisocyanate and catalyst, heat to 80℃ and react for 5 hours, and finally heat to 100℃ and react for 1-2 hours; after the NCO test is qualified, cool down to below 80℃, add neutralizing agent and water, then continue to add water, stir for 1 hour, and obtain self-healing hydrophobic waterborne polyurethane emulsion.

[0017] Beneficial Effects: This invention utilizes hydroxyl silicone oil to provide hydrophobic properties, and dynamic chemical bonds enhance the self-healing properties of the coating at low temperatures. The resulting waterborne polyurethane emulsion is then prepared through self-emulsification. The waterborne polyurethane emulsion prepared by this invention possesses excellent hydrophobicity and self-healing properties, providing longer-lasting protection to the substrate and reducing maintenance costs during use. Detailed Implementation

[0018] The technical solution of the present invention will be described in detail below with reference to the embodiments. The scope of protection of the present invention is not limited to the following embodiments.

[0019] Example 1 This example aims to demonstrate oxime urethane prepolymer A and its synthesis method, as follows: Now, add 300g of acetone and 80g of methylglyoxime to the reactor, heat to 55℃, and add 174.36g of isophorone diisocyanate dropwise at a uniform rate. After reacting for 8 hours, test the NCO. If it is qualified, remove the solvent under reduced pressure and discharge the material for later use.

[0020] Example 2 This example aims to demonstrate the synthesis method of polyurethane emulsions, as follows: Add 120g of polyester glycol 2000 and 80g of polyether glycol 1000 to a reaction vessel, heat to 90℃ and dehydrate under vacuum for 1 hour, add 5g of trimethylolpropane, 10g of dimethylolpropionic acid, 9.02g of hexamethylene diisocyanate, 31.66g of dicyclohexylmethane diisocyanate, and 0.2g of dibutyltin dilaurate, heat to 80℃ and react for 5 hours, then heat to 120℃ and react for 1 hour, cool to 70℃, add 7.54g of triethylamine mixture 100, deionized water, then quickly add 487g of deionized water and stir at high speed for 1 hour to obtain a light blue glossy polyurethane emulsion.

[0021] This polyurethane emulsion has a solids content of 40%, a viscosity of 400-2000 mPa·s, and is stable after 30 days of storage at 40℃. Its acid value (based on solids content) is 16.35 mgKOH / g, and its hydroxyl value (based on solids content) is 42.12 mgKOH / g. When combined with hexamethoxymelamine (CYMEL304), after baking at 140℃ for 30 minutes, it exhibits a pencil hardness of HB, a paint film adhesion grade of 0, a stone chip resistance grade of 2, resistance to water at room temperature for 10 days, acid resistance for 100 hours, and neutral salt spray resistance for 200 hours. After being scratched and cured at 80℃ for 48 hours, its self-healing rate is 10%. This resin is suitable for stone chip resistant automotive chassis topcoats. Example 3 This example aims to demonstrate the synthesis method of polyurethane emulsions with added hydroxyl silicone oil, as follows: Add 120g of polyester glycol 2000, 60g of polyether glycol 1000, and 20g of hydroxyl silicone oil with a molecular weight of 1000 to a reaction vessel. Heat to 90℃ and dehydrate under vacuum for 1 hour. Add 5g of trimethylolpropane, 10g of dimethylolpropionic acid, 9.02g of hexamethylene diisocyanate, 31.66g of dicyclohexylmethane diisocyanate, and 0.2g of dibutyltin dilaurate. Heat to 80℃ and react for 5 hours. Heat to 120℃ and react for 1 hour. Cool to 70℃ and add 7.54g of triethylamine mixed with 100g of deionized water. Then quickly add 487g of deionized water and stir at high speed for 1 hour to obtain a polyurethane emulsion with a light blue luster.

[0022] This polyurethane emulsion has a solids content of 40%, a viscosity of 400-2000 mPa·s, and is stable after 30 days of storage at 40℃. Its acid value (based on solids content) is 16.35 mgKOH / g, and its hydroxyl value (based on solids content) is 42.12 mgKOH / g. When combined with hexamethoxymelamine (CYMEL304), after baking at 140℃ for 30 minutes, it exhibits a pencil hardness of 2H, a paint film adhesion grade of 0, a stone chip resistance grade of 2, resistance to water at room temperature for 20 days, acid resistance for 140 hours, and neutral salt spray resistance for 300 hours. After being scratched and cured at 80℃ for 48 hours, its self-healing rate is 12%. It is suitable as a resin for stone chip resistant automotive chassis topcoats.

[0023] Example 4 This example aims to demonstrate the synthesis method of a polyurethane emulsion with added hydroxyl silicone oil and oxime urethane prepolymer A, as follows: Add 100g of polyester glycol 2000, 60g of polyether glycol 1000, and 20g of hydroxyl silicone oil with a molecular weight of 1000 to a reaction vessel. Heat to 90℃ and dehydrate under vacuum for 1 hour. Add 20g of oxime urethane prepolymer A, 5g of trimethylolpropane, 10g of dimethylolpropionic acid, 9.02g of hexamethylene diisocyanate, 31.66g of dicyclohexylmethane diisocyanate, and 0.3g of dibutyltin dilaurate. Heat to 80℃ and react for 5 hours. Heat to 120℃ and react for 1 hour. Cool to 70℃ and add 7.54g of triethylamine mixture 100g and deionized water. Then quickly add 487g of deionized water and stir at high speed for 1 hour to obtain a light blue glossy polyurethane emulsion.

[0024] This polyurethane emulsion has a solids content of 40%, a viscosity of 400-3000 mPa·s, and is stable after 30 days of storage at 40℃. Its acid value (based on solids content) is 16.35 mg KOH / g, and its hydroxyl value (based on solids content) is 42.12 mg KOH / g. When combined with hexamethoxymelamine (CYMEL304), after baking at 140℃ for 30 minutes, it exhibits a pencil hardness of 2H, a paint film adhesion grade of 0, a stone chip resistance grade of 1, resistance to water at room temperature for 25 days, acid resistance for 140 hours, and neutral salt spray resistance for 300 hours. After being scratched and cured at 80℃ for 48 hours, its self-healing rate is 90%. It is suitable for self-healing resins for stone chip resistant automotive chassis topcoats.

[0025] Example 5 This example aims to demonstrate the synthesis method of polyurethane emulsions by adding different types of polyols along with hydroxyl silicone oil and oxime urethane prepolymer A, as follows: Add 100g of polytetrahydrofuran glycol 2000, 60g of polyester glycol 1000, and 20g of hydroxyl silicone oil with a molecular weight of 1000 to a reaction vessel. Heat to 90℃ and dehydrate under vacuum for 1h. Add 20g of oxime urethane prepolymer A, 5g of trimethylolpropane, 10g of dimethylolpropionic acid, 9.02g of hexamethylene diisocyanate, 31.66g of dicyclohexylmethane diisocyanate, and 0.3g of dibutyltin dilaurate. Heat to 80℃ and react for 5h. Heat to 120℃ and react for 1h. Cool to 70℃ and add 7.54g of triethylamine mixture 100g and deionized water. Then quickly add 487g of deionized water and stir at high speed for 1h to obtain a polyurethane emulsion with a light blue luster.

[0026] This polyurethane emulsion has a solids content of 40%, a viscosity of 400-3000 mPa·s, and is stable after 30 days of storage at 40℃. Its acid value (based on solids content) is 16.35 mgKOH / g, and its hydroxyl value (based on solids content) is 42.12 mgKOH / g. When combined with hexamethoxymelamine (CYMEL304), after baking at 140℃ for 30 minutes, it exhibits a pencil hardness of 2H, a paint film adhesion grade of 0, a stone chip resistance grade of 1, resistance to water at room temperature for 30 days, acid resistance for 200 hours, and neutral salt spray resistance for 400 hours. After being scratched and cured at 80℃ for 48 hours, its self-healing rate is 85%. It is suitable for self-healing resins for stone chip resistant automotive chassis topcoats.

[0027]

[0028] Examples 2, 3, 4, and 5 demonstrate that adding hydroxyl silicone oil significantly improves the hardness and water resistance of the coating film. Furthermore, the introduction of oxime ester bonds significantly enhances the self-healing ability of the coating film. The combination of polytetrahydrofuran polyol and polyester polyol exhibits superior water and salt spray resistance compared to polycarbonate polyol and polyether polyol. This is primarily due to the fact that the ester bonds in polycarbonate are easily hydrolyzed, resulting in poor water and salt spray resistance, while the furan structure in polytetrahydrofuran is less prone to hydrolysis, leading to better water and salt spray resistance.

[0029] This invention uses a normal phase emulsification method to prepare polyurethane emulsions. High-speed dispersion and high shear force are used to quickly disperse the resin into stable latex particles, resulting in small particle size and good stability.

[0030] By introducing hydroxyl silicone oil into the resin chain segment, its excellent hydrophobicity can significantly improve the hydrophobic performance after the coating film is cured. This invention uses dynamic chemical bonds to introduce oxime ester bonds into the main resin chain segment, realizing the self-healing performance of the coating film at low temperatures, extending the service life of the coating film, and significantly saving maintenance costs.

[0031] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a self-healing, hydrophobic aqueous polyurethane emulsion, characterized in that, Includes the following steps: (1) Preparation of prepolymer A containing oxime ester Add acetone solvent and dioxime raw material, heat to 50-55℃, slowly add diisocyanate, keep warm for 6-10 hours after the addition is completed, and after the NCO test is qualified, remove acetone and discharge the material for later use. (2) Add polyol and hydroxyl silicone oil to a four-necked flask, heat to 80-120℃, dehydrate under vacuum for 1 hour, then add crosslinking agent, oxime urethane prepolymer A, and raw materials containing 3-7 parts of carboxyl groups, continue to add diisocyanate and catalyst, heat to 80℃ and react for 5 hours, and finally heat to 100℃ and react for 1-2 hours; after the NCO test is qualified, cool down to below 80℃, add neutralizing agent and water, then continue to add water, stir for 1 hour, and obtain self-healing hydrophobic waterborne polyurethane emulsion.

2. The method for preparing the self-healing hydrophobic aqueous polyurethane emulsion according to claim 1, characterized in that, Includes the following steps: (1) Preparation of prepolymer A containing oxime ester Add 2-10 parts of acetone solvent and 3-5 parts of dioxime raw material, heat to 50-55℃, slowly add 5-10 parts of diisocyanate, keep warm for 6-10 hours after the addition is completed, and after the NCO test is qualified, remove acetone and discharge for later use. (2) Add 10-20 parts of polyol and 1-5 parts of hydroxyl silicone oil to a four-necked flask, heat to 80-120℃, dehydrate under vacuum for 1 hour, then add 1-5 parts of crosslinking agent, 5-10 parts of oxime urethane prepolymer A, and 3-7 parts of carboxyl-containing raw materials, then add 5-20 parts of diisocyanate, add 0.1%-1% of catalyst by total mass, heat to 80℃ and react for 5 hours, then heat to 100℃ and react for 1-2 hours; after the NCO test is qualified, cool down to below 80℃, add 3-5 parts of neutralizing agent and mix with 70 parts of water, then add 100-400 parts of water, stir at high speed for 1 hour, and obtain a self-healing hydrophobic waterborne polyurethane emulsion.

3. The method for preparing the self-healing hydrophobic aqueous polyurethane emulsion according to claim 1, characterized in that: In step (1), the dioxime raw material is one or a mixture of several of the following: dioxime, dimethyl dioxime, acetylacetone dioxime, and cyclohexanedione dioxime.

4. The method for preparing the self-healing hydrophobic aqueous polyurethane emulsion according to claim 1, characterized in that: In step (1), the diisocyanate is one or more of hexamethylene diisocyanate, toluene diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, and diphenylmethane diisocyanate.

5. The method for preparing the self-healing hydrophobic aqueous polyurethane emulsion according to claim 1, characterized in that: The polyol mentioned in step (2) is one or a mixture of several of the following: polyether polyol, polyester polyol, polycarbonate polyol, and polytetrahydrofuran ester polyol.

6. The method for preparing the self-healing hydrophobic aqueous polyurethane emulsion according to claim 1, characterized in that: The hydroxy silicone oil mentioned in step (2) is a hydroxy silicone oil with a molecular weight of 200-2000; the crosslinking agent in step (2) is one or a mixture of ethylenediamine, diethylenetriamine, triethylenetetramine, trihydroxypropane, glycerol, and pentaerythritol.

7. The method for preparing the self-healing hydrophobic aqueous polyurethane emulsion according to claim 1, characterized in that: In step (2), the carboxyl-containing raw material is one or a mixture of two of dimethylolpropionic acid and dimethylolbutyric acid; in step (2), the catalyst is dibutyltin dilaurate.

8. The method for preparing the self-healing hydrophobic aqueous polyurethane emulsion according to claim 1, characterized in that: In step (2), the diisocyanate is one or more of hexamethylene diisocyanate, toluene diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, and diphenylmethane diisocyanate.

9. The method for preparing the self-healing hydrophobic aqueous polyurethane emulsion according to claim 1, characterized in that: The neutralizing agent in step (2) is one or more of ammonia, triethylamine, dimethylethanolamine, and triethanolamine.

10. A self-healing hydrophobic aqueous polyurethane emulsion prepared by any one of claims 1 to 9.

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