Tea polyphenol palmitate modified waterborne polyurethane dispersion as well as preparation method and application thereof

Abstract

The invention provides a tea polyphenol palmitate modified waterborne polyurethane dispersion as well as a preparation method and application thereof. The waterborne polyurethane dispersion is prepared from the following raw materials in percentage by mass on the basis of the solid content mass of waterborne polyurethane resin: 24-34 wt% of polyisocyanate; 48 to 71 wt% of a polyol; 5-8 wt% of tea polyphenol palmitate; 1-6 wt% of a hydrophilic chain extender containing reactive hydrogen; 1-6 wt% of a multifunctional chain extender containing amino groups; 1-8 wt% of an amino silane coupling agent; and 0-1 wt% of a neutralizer. The polyurethane emulsion synthesized by taking tea polyphenol palmitate as a modifier and adopting an acetone method shows excellent yellowing resistance when being applied to industrial paint, and has relatively good base material adhesion.

Description

Technical Field

[0001] The invention belongs to the field of waterborne polyurethane materials, and in particular relates to a tea polyphenol palmitate modified waterborne polyurethane dispersion, a preparation method and a use thereof. Background Art

[0002] The waterborne polyurethane dispersion is further formulated into industrial topcoat and applied to the metal surface. It not only has decorative functions but also has certain protective functions.

[0003] Industrial topcoats are applied on metal surfaces and exposed to the natural environment for a long time. After long-term aging in the natural environment such as light, sun, and rain, they are prone to yellowing, which reduces their aesthetics and, to a certain extent, reduces the protective performance of the paint film. Patent CN109099241A discloses a UV yellowing-resistant matte topcoat and a preparation method thereof. Polyurethane acrylate is used as the main resin, and palmitic acid is added as an anti-yellowing agent to prepare a matte topcoat with excellent yellowing resistance. However, in the patent, palmitic acid is added in a physical blending manner, which is easy to migrate and precipitate, and the coating stability is poor.

[0004] Based on the current market requirements for environmental protection of industrial topcoats, the performance requirements for water-based industrial topcoats are getting higher and higher. As the main raw material for industrial topcoats, it is necessary to improve the comprehensive performance of water-based polyurethane. The formulated industrial topcoats are required to be exposed to the outdoors for a long time. Based on this, it is very necessary to improve the yellowing resistance of the topcoat. Summary of the invention

[0005] In view of the deficiencies in the prior art, the object of the present invention is to provide a tea polyphenol palmitate modified aqueous polyurethane dispersion and a preparation method thereof, which can improve the yellowing resistance of industrial topcoats.

[0006] The tea polyphenol palmitate modified waterborne polyurethane dispersion of the present invention provides a new solution for solving the problems of yellowing resistance, substrate adhesion and film strength of current industrial paint films.

[0007] To achieve the above objectives, the present invention adopts the following technical solutions:

[0008] On the one hand, the present invention provides a tea polyphenol palmitate modified aqueous polyurethane dispersion, which is prepared from raw materials comprising the following mass percentages based on the solid content of the aqueous polyurethane resin:

[0009] A) polyisocyanate, 24-34 wt%, preferably 28-30 wt%;

[0010] B) polyol, 48-71 wt%, preferably 58-62 wt%;

[0011] C) tea polyphenol palmitate, 5-8wt%, preferably 6.5wt%;

[0012] D) a hydrophilic chain extender containing active hydrogen, 1-6 wt%, preferably 1.5-4 wt%;

[0013] E) a multifunctional chain extender containing amino groups, 1-6 wt%, preferably 2-5 wt%;

[0014] F) aminosilane coupling agent, 1-8wt%, preferably 2-6wt%;

[0015] G) Neutralizing agent, 0-1 wt%, preferably 0.4-0.6 wt%.

[0016] Specifically, it is prepared from raw materials comprising the following mass percentage compositions:

[0017] A) polyisocyanate includes but is not limited to 24wt%, 25wt%, 26wt%, 27wt%, 28wt%, 29wt%, 30wt%, 31wt%, 32wt%, 33wt%, 34wt%, etc.;

[0018] B) polyols include but are not limited to 48wt%, 50wt%, 52wt%, 54wt%, 56wt%, 58wt%, 60wt%, 62wt%, 64wt%, 66wt%, 68wt%, 70wt%, 71wt%, etc.;

[0019] C) tea polyphenol palmitate includes but is not limited to 5wt%, 5.5wt%, 6wt%, 6.5wt%, 7wt%, 7.5wt%, 8wt%, etc.;

[0020] D) hydrophilic chain extenders containing active hydrogen include but are not limited to 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, etc.;

[0021] E) amino-containing multifunctional chain extenders including but not limited to 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, etc.;

[0022] F) aminosilane coupling agents include but are not limited to 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, etc.;

[0023] G) Neutralizing agents include, but are not limited to, 0 wt%, 0.05 wt%, 0.2 wt%, 0.4 wt%, 0.6 wt%, 0.8 wt%, 1 wt%, and the like.

[0024] In the present invention, the NCO% content of the polyisocyanate in component A) is 30-50%;

[0025] Preferably, the polyisocyanate is selected from one or more of aliphatic polyisocyanates and alicyclic isocyanates, preferably one or more of isophorone diisocyanate, 1,6-hexyl diisocyanate, and dicyclohexylmethane diisocyanate.

[0026] In the present invention, the polyol in component B) is a polyol with a number average molecular weight of 100-5000 and a functionality of 2-4;

[0027] Preferably, the polyol is selected from one or more of polypropylene glycol, polyethylene glycol, and polytetramethylene glycol.

[0028] In the present invention, the hydrophilic chain extender containing active hydrogen in component D) is selected from one or more of dihydroxypropionic acid, dimethylolbutyric acid, dimethylolvaleric acid, dimethyloloctanoic acid, 1,2-propylene glycol-3-sodium sulfonate, and 1,4-butanediol-2-sodium sulfonate.

[0029] In the present invention, the amino-containing multifunctional chain extender of component E) is selected from hydrazide chain extenders, preferably one or more of succinic acid hydrazide, sebacic acid hydrazide, adipic acid dihydrazide, benzoic acid hydrazide, isophthalic acid hydrazide and p-hydroxybenzoic acid hydrazide.

[0030] In the present invention, the aminosilane coupling agent of component F) is selected from one or more of γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, N-β(aminoethyl)-γ-aminopropyltrimethoxysilane, and aminoethylaminoethylaminopropyltrimethoxysilane.

[0031] In the present invention, the neutralizing agent in component G) is selected from alkaline compounds, preferably one or more of sodium hydroxide, potassium hydroxide, triethylamine and ammonia water.

[0032] In the present invention, the solid content of the tea polyphenol palmitate modified aqueous polyurethane dispersion is 50-70wt%, and the rest is water dispersant.

[0033] In the present invention, the particle size of the tea polyphenol palmitate modified aqueous polyurethane dispersion is 200-400 nm, preferably 300 nm.

[0034] Another aspect of the present invention provides a method for preparing the tea polyphenol palmitate modified aqueous polyurethane dispersion.

[0035] The tea polyphenol palmitate modified aqueous polyurethane dispersion is prepared by adding tea polyphenol palmitate to perform modification in the isocyanate prepolymerization reaction stage.

[0036] Tea polyphenol palmitate contains hydroxyl groups, which can react with the isocyanate NCO group in the system and participate in the chain extension of the system. Since tea polyphenol palmitate is a high-functionality structure, it can form a highly cross-linked system during the reaction with isocyanate. The resulting resin not only has excellent yellowing resistance, but also has high bulk strength and paint film adhesion.

[0037] In addition, in the present invention, a silane coupling agent and a multifunctional chain extender containing an amino group, such as a hydrazide chain extender, are added in the post-chain extension stage to extend the chain, and the adhesion of the synthesized waterborne polyurethane to the substrate is further improved.

[0038] Specifically, a method for preparing a tea polyphenol palmitate modified aqueous polyurethane dispersion comprises the following preparation steps:

[0039] (1) mixing component A) polyisocyanate and component B) polyol to react to obtain a prepolymer, and then adding acetone to mix uniformly;

[0040] (2) adding component C) tea polyphenol palmitate, component D) a hydrophilic chain extender containing active hydrogen, component E) a multifunctional chain extender containing amino groups, and component F) an aminosilane coupling agent to the system of step (1) to carry out a reaction;

[0041] (3) Adding component G) the neutralizing agent to the system of step (2) and stirring, then adding acetone and mixing evenly, adding deionized water to disperse under high-speed shearing, removing acetone, and obtaining the tea polyphenol palmitate modified waterborne polyurethane dispersion.

[0042] The above-mentioned preparation method provided by the present invention is a commonly used acetone method in the field. Specifically, the relevant operations and process conditions in the preparation method of the present invention, and the devices used therein, can be carried out by using the corresponding conventional selections in the field, and there is no particular limitation thereto. The technicians can optimize the known processes in the prior art according to actual needs. Specifically, for example, the following conditions listed in the present invention can be used:

[0043] In the present invention, the reaction in step (1) is carried out at a temperature of 80-90° C. and for a time of 0.8-1.2 h.

[0044] In the present invention, the amount of acetone added in step (1) is 20-25% of the total mass of component A) polyisocyanate and component B) polyol.

[0045] In the present invention, the reaction temperature in step (2) is 60-80°C;

[0046] Specifically, the reaction ends when the theoretical NCO% is reached; the theoretical NCO content is a conventional method for determining the end point of the reaction of isocyanate and polyol in the art, and can be calculated by technicians based on the ratio of the effective content of isocyanate and polyol.

[0047] In the present invention, in the reaction of step (2), a catalyst is further added to the system, and the catalyst is selected from an organic bismuth catalyst, such as one or more of bismuth isooctanoate, bismuth laurate, and bismuth neodecanoate, preferably one or more of organic bismuth Coscat83, organic bismuth 1610, organic bismuth 2010, organic bismuth 2810, and organic bismuth 2808;

[0048] Preferably, the amount of the catalyst added is 0.2-0.6% by weight of the solid content in the reaction system.

[0049] In the present invention, the stirring time in step (3) is 3-8 minutes, and the temperature is preferably lowered to 30-35° C. after neutralization.

[0050] In the present invention, the acetone is added in step (3) for dilution to reduce viscosity. The amount of acetone added does not need to be precisely controlled and can be obtained by technicians based on experience. It is usually about 25wt% of the total solids. For example, based on the solid raw material, the amount of acetone added can be 20-30wt%.

[0051] In the present invention, step (3) further includes adding deionized water to disperse and removing acetone under high-speed shearing, which are conventional operations in the field and are not specifically required here;

[0052] Specifically, the amount of deionized water added is such that the solid content of the tea polyphenol palmitate modified aqueous polyurethane dispersion is 50-70wt%.

[0053] In another aspect, the present invention provides application of the tea polyphenol palmitate modified aqueous polyurethane dispersion.

[0054] The tea polyphenol palmitate modified waterborne polyurethane dispersion of the present invention has excellent yellowing resistance, substrate adhesion and paint film strength, and can be used in the fields of printing coatings, architectural coatings, industrial paint topcoats, and is particularly suitable for the field of industrial paint topcoats.

[0055] Compared with the prior art, the present invention has the following positive effects:

[0056] The present invention adopts tea polyphenol palmitate as a modifier, so that the obtained waterborne polyurethane has excellent yellowing resistance. At the same time, the substrate adhesion and the strength of the paint film can be improved by cooperating with components such as silane coupling agents. DETAILED DESCRIPTION

[0057] The following examples will further illustrate the method provided by the present invention, but the present invention is not limited to the listed examples, and should also include any other known changes within the scope of the rights claimed by the present invention.

[0058] Unless otherwise specified, the reagents, materials and instruments used in the following examples are conventional reagents, conventional materials and conventional instruments in the art and can be obtained commercially.

[0059] The main test methods used for the characteristic parameters of the waterborne polyurethane dispersion in the embodiments of the present invention are as follows:

[0060] Particle size test method: Malvern ZetaSizer Nano-ZS90 laser particle size analyzer from Malvern, UK, was used to dilute the emulsion by 5%, and then the test was conducted at room temperature (about 25°C), with a detection angle of 90° and a laser wavelength of 633nm to test the particle size of the sample.

[0061] Solid content test method: Take a clean and dry tin foil container and weigh it with an analytical balance as w1. Use the reduction method to weigh 1.5-2 grams of sample emulsion into the weighed tin foil container, record the weight of the sample emulsion as w2, then put it into a 140℃ oven to dry for 30 minutes, take it out and weigh it again as w3. Weigh each time until the weight difference between the two weighings is ≤0.01 grams (accurate to 0.01 grams). Solid content = (w3-w1) / w2×100%.

[0062] The main sources of raw materials used in the examples of the present invention are as follows:

[0063] HMDI (dicyclohexylmethane diisocyanate, NCO% content is about 32.0%, Wanhua Chemical Group Co., Ltd.);

[0064] IPDI (isophorone diisocyanate, NCO% content is about 37.8%, Wanhua Chemical Group Co., Ltd.);

[0065] PPG2000 (polypropylene glycol, number average molecular weight ≈ 2000, functionality 2, Dongda Chemical);

[0066] PTMG2000 (polytetramethylene glycol, number average molecular weight 2000, functionality 2, Yantai Huada Chemical);

[0067] PTMG1000 (polytetramethylene glycol, number average molecular weight 1000, functionality 2, Yantai Huada Chemical);

[0068] Tea polyphenol palmitate (Ningbo Kangle Biotechnology Co., Ltd., purity >98%), functionality 8;

[0069] Sebacic acid dihydrazide (Shanghai Aladdin Biochemical Technology Co., Ltd., purity 96%);

[0070] ADH (adipic acid dihydrazide, Shandong Dengnuo New Materials Co., Ltd., analytical grade);

[0071] Isophthalic acid hydrazide (Zhejiang Runtu Co., Ltd., analytical grade);

[0072] γ-Aminopropyltriethoxysilane (Shandong Sike New Materials Co., Ltd., analytical grade);

[0073] γ-Aminopropyltrimethoxysilane (Shandong Sike New Materials Co., Ltd., analytical grade);

[0074] Aminoethylaminoethylaminopropyltrimethoxysilane (Shandong Sike New Materials Co., Ltd., analytical grade);

[0075] Triethylamine (Nantong Runfeng Petrochemical Co., Ltd., analytical grade);

[0076] Ammonia (Dezhou Wanyu Chemical Products Co., Ltd., industrial grade);

[0077] Organobismuth Coscat83: Leading Chemical Company, USA, analytical grade);

[0078] U605 (polyurethane associative thickener, Wanhua Chemical Group Co., Ltd.).

[0079] Example 1

[0080] (1) Into a four-necked flask equipped with a reflux condenser, a thermometer and a mechanical stirrer, 36 g of IPDI, 20 g of HMDI, 36 g of PPG2000, 40 g of PTMG2000 and 36 g of PTMG1000 were added, and the mixture was reacted at 85° C. for 1 h to obtain a prepolymer, to which 40 g of acetone was added to reduce the viscosity.

[0081] (2) Cooling to 60°C, adding 12g of tea polyphenol palmitate, 4g of dihydroxymethylbutyric acid, 8g of sebacic acid hydrazide, and 6g of γ-aminopropyltriethoxysilane, and adding organic bismuth Coscat83 with a solid content of 0.4wt% to the reaction system, stirring evenly, heating to 70°C for reaction, and cooling when the reaction reaches the theoretical NCO%.

[0082] (3) Add 0.4 g of triethylamine and stir for 5 min, add 50 g of acetone to dilute, stir and mix for 5 min, and continue to cool to 35° C., add 198 g of deionized water under high-speed shearing to disperse, remove acetone, and obtain a tea polyphenol palmitate modified waterborne polyurethane dispersion.

[0083] The tea polyphenol palmitate modified aqueous polyurethane dispersion has a solid content of 50wt% and a particle size of 300-400nm.

[0084] Example 2

[0085] (1) Into a four-necked flask equipped with a reflux condenser, a thermometer and a mechanical stirrer, 32 g of IPDI, 30 g of HMDI, 20 g of PPG2000, 48 g of PTMG2000 and 40 g of PTMG1000 were added, and the mixture was reacted at 80° C. for 0.8 h to obtain a prepolymer, to which 40 g of acetone was added to reduce the viscosity.

[0086] (2) Cool down to 60°C, add 10g of tea polyphenol palmitate, 8g of dihydroxymethylbutyric acid, 6g of adipic dihydrazide, and 8g of γ-aminopropyltriethoxysilane, and add organic bismuth Coscat83 with a solid content of 0.4wt% to the reaction system, stir evenly, heat to 75°C for reaction, and cool down when the reaction reaches the theoretical NCO%.

[0087] (3) Add 0.8 g of triethylamine and stir for 5 min, add 43 g of acetone to dilute, stir and mix for 5 min, and continue to cool to 32° C., add 172 g of deionized water under high-speed shearing to disperse, remove acetone, and obtain a tea polyphenol palmitate modified waterborne polyurethane dispersion.

[0088] The tea polyphenol palmitate modified aqueous polyurethane dispersion has a solid content of 50wt% and a particle size of 300-400nm.

[0089] Example 3

[0090] (1) Into a four-necked flask equipped with a reflux condenser, a thermometer and a mechanical stirrer, 20 g of IPDI, 40 g of HMDI, 40 g of PPG2000, 20 g of PTMG2000 and 36 g of PTMG1000 were added, and the mixture was reacted at 90° C. for 1.2 h to obtain a prepolymer, to which 40 g of acetone was added to reduce the viscosity.

[0091] (2) Cool down to 60°C, add 14g of tea polyphenol palmitate, 10g of dihydroxymethylbutyric acid, 12g of isophthalic acid hydrazide, and 10g of γ-aminopropyltrimethoxysilane, and add organic bismuth Coscat83 with a solid content of 0.5wt% to the reaction system, stir evenly, heat to 80°C for reaction, and cool down when the reaction reaches the theoretical NCO%.

[0092] (3) Add 0.4 g of ammonia water and stir for 5 min, add 50 g of acetone to dilute, stir and mix for 5 min, and continue to cool to 30° C., add 202 g of deionized water under high-speed shearing to disperse, remove acetone, and obtain a tea polyphenol palmitate modified waterborne polyurethane dispersion.

[0093] The tea polyphenol palmitate modified aqueous polyurethane dispersion has a solid content of 50wt% and a particle size of 300-400nm.

[0094] Example 4

[0095] (1) Into a four-necked flask equipped with a reflux condenser, a thermometer and a mechanical stirrer, 28 g of IPDI, 28 g of HMDI, 20 g of PPG2000, 36 g of PTMG2000 and 48 g of PTMG1000 were added, and the mixture was reacted at 85° C. for 1 h to obtain a prepolymer, to which 40 g of acetone was added to reduce the viscosity.

[0096] (2) Cool down to 60°C, add 18g of tea polyphenol palmitate, 6g of dihydroxymethylbutyric acid, 8g of sebacic acid hydrazide, and 12g of γ-aminopropyltrimethoxysilane, and add organic bismuth Coscat83 with a solid content of 0.6wt% to the reaction system, stir evenly, heat to 70°C for reaction, and cool down when the reaction reaches the theoretical NCO%.

[0097] (3) Add 1.2 g of ammonia water and stir for 5 min, add 50 g of acetone to dilute, stir and mix for 5 min, and continue to cool to 35° C., add 205 g of deionized water under high-speed shearing to disperse, remove acetone, and obtain a tea polyphenol palmitate modified waterborne polyurethane dispersion.

[0098] The tea polyphenol palmitate modified aqueous polyurethane dispersion has a solid content of 50wt% and a particle size of 300-400nm.

[0099] Comparative Example 1

[0100] The method of Example 1 is followed, except that component C) tea polyphenol palmitate is not added in step (2), and other operations and conditions remain unchanged to obtain an aqueous polyurethane dispersion.

[0101] Comparative Example 2

[0102] The method of Example 1 is followed, except that in step (2), component C) tea polyphenol palmitate is replaced by an equimolar amount of palmitate, and other operations and conditions remain unchanged to obtain an aqueous polyurethane dispersion.

[0103] Comparative Example 3

[0104] The method of Example 1 is used with the exception that aminopropyltriethoxysilane is not added in step (2), and other operations and conditions remain unchanged to obtain an aqueous polyurethane dispersion.

[0105] Application performance test of the aqueous polyurethane dispersions prepared in Examples 1-4 and Comparative Examples 1-3 in industrial topcoats:

[0106] Specifically, the aqueous polyurethane dispersions of the embodiment and the comparative example were used to prepare industrial topcoats, and the formulas were shown in Table 1 below:

[0107] Table 1 Waterborne polyurethane construction formula

[0108]

[0109] Mix the raw materials in Table 1, apply them on the metal plate with a brush, and cure them at room temperature 25°C for 24 hours or in an oven at 50°C for 12 hours to obtain the test sample. Then, use the following method to test its performance. The results are shown in Table 2:

[0110] Viscosity test method: Use a BROOKFIELD DV2T touch screen viscometer, use a No. 63 rotor, room temperature 25°C, and a rotation speed of 30 rpm to test the viscosity, and read the reading after the test stops.

[0111] Tensile strength test method: Take a 15cm*15cm, 1mm thick cured sheet mold, pour the synthesized PUD into the mold, cure in a 50℃ oven for 12h, take it out and dry it in an 80℃ oven for 2h to obtain a cured PUD film, cut it with a dumbbell-shaped cutter, and use a tensile testing machine to test its tensile strength.

[0112] Adhesion: Adhesion is tested by the 100-grid method. The width of the 100-grid knife is about 10mm to 12mm, and the interval is 1mm to 1.2mm. There are 10 grids in total. When a straight line is drawn, 10 straight line marks with the same interval will appear. Draw at the vertical position of the straight line marks, and it will become a 100-grid square of 10*10. After the 100-grid knife is drawn, use tape to test whether it will fall off. Stick the tape to the 100-grid position, press it down with your fingers to attach it tightly, and then tear off the tape with a momentary force. Visually check whether the paint on the material has fallen off. Evaluate according to ISO 2409 standard.

[0113] Yellowing test method: Place the sample in the QUV-B equipment for aging. The aging conditions are: light wavelength 313nm, irradiation intensity 0.71W / m 2 , aging temperature 60℃, aging 2000h. After taking out, use Hunterlab colorimeter, light reflection mode to measure ASTM YIE313 (yellowness) of the paint film sample.

[0114] Table 1 Performance comparison between examples and comparative examples

[0115]

Claims

1. A tea polyphenol palmitate modified aqueous polyurethane dispersion, characterized in that: Based on the solid content of the waterborne polyurethane resin, it is prepared from raw materials containing the following mass percentages: A) polyisocyanate, 24-34 wt%, preferably 28-30 wt%; B) polyol, 48-71 wt%, preferably 58-62 wt%; C) tea polyphenol palmitate, 5-8wt%, preferably 6.5wt%; D) a hydrophilic chain extender containing active hydrogen, 1-6 wt%, preferably 1.5-4 wt%; E) a multifunctional chain extender containing amino groups, 1-6 wt%, preferably 2-5 wt%; F) aminosilane coupling agent, 1-8wt%, preferably 2-6wt%; G) Neutralizing agent, 0-1 wt%, preferably 0.4-0.6 wt%.

2. The tea polyphenol palmitate modified aqueous polyurethane dispersion according to claim 1, characterized in that: The NCO% content of the polyisocyanate in component A) is 30-50%; Preferably, the polyisocyanate is selected from one or more of aliphatic polyisocyanates and alicyclic isocyanates, preferably one or more of isophorone diisocyanate, 1,6-hexyl diisocyanate, and dicyclohexylmethane diisocyanate.

3. The tea polyphenol palmitate modified aqueous polyurethane dispersion according to claim 1, characterized in that: Component B) The polyol is a polyol with a number average molecular weight of 100-5000 and a functionality of 2-4; Preferably, the polyol is selected from one or more of polypropylene glycol, polyethylene glycol, and polytetramethylene glycol.

4. The tea polyphenol palmitate modified aqueous polyurethane dispersion according to claim 1, characterized in that: Component D) The hydrophilic chain extender containing active hydrogen is selected from one or more of dihydroxypropionic acid, dimethylolbutyric acid, dimethylolpentanoic acid, dimethyloloctanoic acid, 1,2-propylene glycol-3-sodium sulfonate, and 1,4-butanediol-2-sodium sulfonate.

5. The tea polyphenol palmitate modified aqueous polyurethane dispersion according to claim 1, characterized in that: Component E) The amino-containing multifunctional chain extender is selected from hydrazide chain extenders, preferably one or more of succinic acid hydrazide, sebacic acid hydrazide, adipic acid dihydrazide, benzoic acid hydrazide, isophthalic acid hydrazide and p-hydroxybenzoic acid hydrazide.

6. The tea polyphenol palmitate modified aqueous polyurethane dispersion according to claim 1, characterized in that: Component F) the aminosilane coupling agent is selected from one or more of γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, N-β (aminoethyl)-γ-aminopropyltrimethoxysilane, aminoethylaminoethylaminopropyltrimethoxysilane; and / or Component G) The neutralizing agent is selected from alkaline compounds, preferably one or more of sodium hydroxide, potassium hydroxide, triethylamine, and ammonia water.

7. The tea polyphenol palmitate modified aqueous polyurethane dispersion according to claim 1, characterized in that: Solid content is 50-70wt%, the rest is water dispersant; and / or The particle size is 200-400nm.

8. A method for preparing the tea polyphenol palmitate modified aqueous polyurethane dispersion according to any one of claims 1 to 7, characterized in that the steps include: (1) mixing component A) polyisocyanate and component B) polyol to react to obtain a prepolymer, and then adding acetone to mix uniformly; (2) adding component C) tea polyphenol palmitate, component D) a hydrophilic chain extender containing active hydrogen, component E) a multifunctional chain extender containing amino groups, and component F) an aminosilane coupling agent to the system of step (1) to carry out a reaction; (3) Adding component G) the neutralizing agent to the system of step (2) and stirring, then adding acetone and mixing evenly, adding deionized water to disperse under high-speed shearing, removing acetone, and obtaining the tea polyphenol palmitate modified waterborne polyurethane dispersion.

9. The preparation method according to claim 8, characterized in that: The reaction in step (1) is carried out at a temperature of 80-90°C for a time of 0.8-1.2h; and / or The amount of acetone added in step (1) is 20-25% of the total mass of component A) polyisocyanate and component B) polyol; and / or The reaction temperature in step (2) is 60-80°C; preferably, the reaction ends when the theoretical NCO% is reached; and / or In the reaction of step (2), a catalyst is further added to the system, and the catalyst is selected from an organic bismuth catalyst; Preferably, the amount of the catalyst added is 0.2-0.6% by weight of the solid content in the reaction system; and / or The stirring time in step (3) is 3-8 minutes.

10. The use of the tea polyphenol palmitate modified aqueous polyurethane dispersion described in any one of claims 1 to 7 or the tea polyphenol palmitate modified aqueous polyurethane dispersion prepared by the method described in claim 8 or 9 in the fields of printing coatings, architectural coatings, and industrial paint topcoats, especially in the field of industrial paint topcoats.

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