Waterproof polyurethane composite coating and preparation process thereof

Abstract

The present application relates to the technical field of polyurethane coating, in particular to a waterproof polyurethane composite coating and a preparation process thereof. The preparation process of the waterproof polyurethane composite coating comprises the following steps: preparing quercetin grafted composite filler, preparing modified isophorone diisocyanate solution and preparing polyurethane composite coating. In the present application, polybutylene adipate, dimethylol butyric acid and dibutyltin dilaurate are mixed with the modified isophorone diisocyanate solution to carry out pre-polymerization, then 2-hydroxy-5-substituted long-chain fatty acyloxy methyl benzoate is added to carry out reaction, long-chain fatty acyloxy and methyl benzoate structure are introduced into the polyurethane molecular chain, trimethylolpropane is added to carry out crosslinking reaction, finally, 1,4-butanediol is added as a chain extender to react with the remaining -NCO to prepare the polyurethane composite coating, which can effectively improve the water resistance and adhesion of the polyurethane composite coating.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of polyurethane coatings, in particular to a waterproof polyurethane composite coating and a preparation process thereof. BACKGROUND

[0002] Waterborne polyurethane (WPU) has been widely used as a surface coating of automotive electronic devices and vehicle body materials due to its excellent mechanical properties, abrasion resistance and corrosion resistance, which not only forms an additional protective and external stress bearing area on the surface of the substrate, but also repairs material defects and improves surface roughness due to its excellent flexibility.

[0003] In the preparation process of waterborne polyurethane, in order to achieve its dispersibility in water, hydrophilic groups such as carboxyl groups in dimethylol butyric acid need to be introduced, which form ionic structures by neutralization (such as reaction with triethylamine to form carboxylate), so that the polyurethane molecules can be stably dispersed in water, but after film formation, these hydrophilic groups do not completely disappear and remain in the coating, when the coating contacts moisture, the hydrophilic groups will form hydrogen bonds or polar attraction with water molecules, resulting in the adsorption of water molecules on the surface of the coating or even into the interior, thereby reducing the water resistance; in addition, the molecular chain of waterborne polyurethane is composed of soft segments and hard segments, among which the soft segments account for a high proportion and have low bond energy, which are easily oxidized to form peroxide at high temperature, thereby causing molecular chain rupture, resulting in poor heat aging resistance; and ultraviolet light can directly damage the chemical bonds of the molecular chain of waterborne polyurethane, causing the coating to degrade, and the compatibility of directly adding an ultraviolet resistance agent in a waterborne system is poor, which is easy to migrate or volatilize with moisture, resulting in ineffective inhibition of molecular chain aging and degradation at high temperature, further aggravating the aging of the coating.

[0004] Therefore, it is necessary to provide a waterproof polyurethane composite coating with heat aging and ultraviolet aging resistance and a preparation process thereof to prolong its service life. SUMMARY

[0005] In view of the deficiencies in the prior art, the present application aims to provide a waterproof polyurethane composite coating and a preparation process thereof.

[0006] The present application provides a preparation process of a waterproof polyurethane composite coating, comprising the following steps:

[0007] S1: preparing a quercetin grafted composite filler

[0008] After the magnesium nitrate hexahydrate and aluminum nitrate nonahydrate are dissolved, they are mixed with a nano-silica dispersion liquid, then a mixed alkali solution is added for reaction, and after hydrothermal crystallization, 3-aminopropyl triethoxysilane is used for amination modification, and finally a grafting reaction with quercetin is carried out to obtain a quercetin grafted composite filler;

[0009] S2: Preparation of modified isophorone diisocyanate solution

[0010] After dissolving 3,5-di-tert-butyl-4-hydroxybenzoic acid, isophorone diisocyanate is added for reaction to obtain a modified isophorone diisocyanate solution;

[0011] S3: Preparation of polyurethane composite coating

[0012] S3.1: Polybutylene glycol adipate, dimethylol butyric acid and dibutyltin dilaurate are added to the above modified isophorone diisocyanate solution, and heated and stirred at 65-70°C for 3-4h to obtain a prepolymer;

[0013] S3.2: 2-hydroxy-5-substituted long-chain fatty acyl oxybenzoic acid methyl ester is added to the above prepolymer, and stirred and reacted for 2-3h, and then trimethylolpropane is added and reacted for another 2-3h to obtain a precursor solution;

[0014] S3.3: 1,4-butanediol is added to the above precursor solution, and stirred and reacted for 1-2h, and then triethylamine and acetone are added when the temperature is lowered to 35°C, and stirred and mixed, and then the above quercetin grafted composite filler is added, and stirred and mixed until uniform, and then water is added for emulsification to obtain a polyurethane composite coating.

[0015] Further, S1 specifically comprises the following steps:

[0016] S1.1: Nano-silicon dioxide is added to deionized water at a ratio of 1g: (40-50)mL, and ultrasonically dispersed for 30-40min to obtain a nano-silicon dioxide dispersion;

[0017] S1.2: Magnesium nitrate hexahydrate and aluminum nitrate nonahydrate are added to deionized water at a ratio of (1.7-1.8)g: 1g: (10-16)mL, and after being fully stirred and dissolved, the above nano-silicon dioxide dispersion is added, and stirred and mixed, and then a mixed alkali solution is added at a rate of 2-4mL / min to adjust the pH to 9-10, and stirring is continued for 1-2h to obtain a precursor solution;

[0018] S1.3: The above precursor solution is transferred to a high-pressure reaction kettle, and crystallized at 75-85°C for 10-12h, and then naturally cooled to room temperature, and then centrifuged, washed to neutral, vacuum dried and ground to obtain a composite filler;

[0019] S1.4: 3-aminopropyltriethoxysilane is added into a 90% volume fraction ethanol solution at 1 g: (100-200) mL, and glacial acetic acid is added to adjust the pH to 4-5, and hydrolysis is stirred for 20-30 min, then the above-mentioned composite filler is added at 1 g: (10-20) mL, and heated and stirred at 50-60°C for 4-5 h, and after cooling, centrifugal separation, washing and vacuum drying, the aminated composite filler is obtained;

[0020] S1.5: quercetin, p-toluenesulfonic acid and hydroquinone are added into anhydrous ethanol at (0.8-1) g: (0.05-0.1) g: 0.01 g: (90-100) mL, and after heated and stirred to dissolve at 50-60°C, the above-mentioned aminated composite filler is added at 1 g: (20-30) mL, and heated and stirred to reflux at 70-80°C under nitrogen protection for 5-6 h, and after cooling, centrifugal separation, washing and vacuum drying, the quercetin grafted composite filler is obtained.

[0021] Further, S2 specifically comprises the following steps:

[0022] S2.1: 3,5-di-tert-butyl-4-hydroxybenzoic acid is added into anhydrous acetone at 1 g: (10-20) mL, and heated and stirred to dissolve at 50-60°C, to obtain a 3,5-di-tert-butyl-4-hydroxybenzoic acid solution;

[0023] S2.2: when the above-mentioned 3,5-di-tert-butyl-4-hydroxybenzoic acid solution is cooled to 40°C, 2,6-di-tert-butyl-p-cresol and dibutyltin dilaurate are added, stirred and mixed, then isophorone diisocyanate is added at 3-5 mL / min, and heated to react at 60-65°C for 2.5-3.5 h under nitrogen protection, to obtain a modified isophorone diisocyanate solution.

[0024] Further, the mass ratio of nano-silicon dioxide to magnesium nitrate hexahydrate is 1: (8-10).

[0025] Further, the mixed alkali solution is prepared by dissolving sodium hydroxide and sodium carbonate in deionized water at a solid-liquid ratio of (3.8-4) g: 1 g: (45-50) mL.

[0026] Further, the amount of dibutyltin dilaurate added is 0.3-0.4% of the mass of 3,5-di-tert-butyl-4-hydroxybenzoic acid.

[0027] Further, the amount of 2,6-di-tert-butyl-p-cresol and dibutyltin dilaurate added is equal.

[0028] Further, the molar ratio of isophorone diisocyanate to 3,5-di-tert-butyl-4-hydroxybenzoic acid is 2:1.

[0029] Further, the raw material composition of the polyurethane composite coating is 90-100 parts of polybutylene adipate, 70-80 parts of modified isophorone diisocyanate solution, 10-12 parts of quercetin grafted composite filler, 9-11 parts of dimethylol butyric acid, 7-9 parts of 2-hydroxy-5-substituted long-chain fatty acyloxy benzoic acid methyl ester, 5-6 parts of trimethylolpropane, 3-5 parts of 1,4-butanediol, 0.06-0.1 parts of dibutyltin dilaurate, 1.4-1.8 parts of triethylamine, 20-30 parts of acetone and 50-60 parts of water in mass fraction.

[0030] A waterproof polyurethane composite coating prepared by the preparation process of any one of the waterproof polyurethane composite coatings described above.

[0031] The present application has the following advantages:

[0032] 1, In the present application, by mixing polybutylene adipate, dimethylol butyric acid and dibutyltin dilaurate with modified isophorone diisocyanate solution for pre-polymerization, then adding 2-hydroxy-5-substituted long-chain fatty acyloxy benzoic acid methyl ester for reaction, long-chain fatty acyloxy and benzoic acid methyl ester structures are introduced into the polyurethane molecular chain, and trimethylolpropane is added for crosslinking reaction to increase the crosslinking degree of the molecular chain, and finally 1,4-butanediol is added as a chain extender to react with the remaining -NCO, and after neutralization with triethylamine, viscosity reduction with acetone and emulsification with water to form the polyurethane composite coating, the introduction of long-chain fatty acyloxy will enrich on the surface of the coating, forming a hydrophobic barrier to reduce the penetration of water molecules in the coating, and also reducing the surface energy of the coating, thereby effectively improving the water resistance of the polyurethane composite coating, at the same time, the polar groups in 2-hydroxy-5-substituted long-chain fatty acyloxy benzoic acid methyl ester can interact with the substrate to enhance the interfacial bonding strength, the long-chain structure can increase the flexibility and entanglement ability of the polyurethane molecular chain, improve the cohesion of the coating, and the aromatic ring in the benzoic acid methyl ester structure can enhance the intermolecular interaction, further improve the bonding stability of the coating and the substrate, so as to effectively improve the adhesion of the polyurethane composite coating.

[0033] 2. In this invention, after dissolving 3,5-di-tert-butyl-4-hydroxybenzoic acid, isophorone diisocyanate is added under the catalysis of dibutyltin dilaurate to react, thereby introducing 3,5-di-tert-butyl-4-hydroxybenzoic acid into the isophorone diisocyanate molecule to obtain modified isophorone diisocyanate. After the modified isophorone diisocyanate is made into a polyurethane composite coating with polybutylene adipate, etc., 3,5-di-tert-butyl-4-hydroxybenzoic acid can be oxidized at high temperature to generate free radical reaction, terminating the free radical chain oxidation reaction, inhibiting the oxidative degradation of the coating, and thus improving its heat aging resistance. At the same time, the introduction of tert-butyl and benzene ring structures in 3,5-di-tert-butyl-4-hydroxybenzoic acid can further enhance the hydrophobicity of the molecular chain, thereby improving the water resistance of the coating.

[0034] 3. In this invention, magnesium nitrate hexahydrate and aluminum nitrate nonahydrate are dissolved, mixed with a nano-silica dispersion, and a mixed alkaline solution is added for co-precipitation. Then, hydrothermal crystallization is performed via a high-pressure hydrothermal reaction to prepare a composite filler. Next, 3-aminopropyltriethoxysilane is used for amination and surface modification, followed by a reaction with quercetin to graft quercetin onto the surface of the composite filler. After obtaining the quercetin-grafted composite filler, quercetin can be uniformly dispersed in the coating matrix along with the composite filler carrier. Furthermore, after quercetin is chemically grafted onto the surface of the composite filler, it can be carried by the carrier... The matrix is ​​"woven" into a cross-linked network, and migration requires the breaking of chemical bonds. Therefore, it can inhibit the migration of quercetin in the coating matrix, thereby effectively improving the long-term UV aging resistance of the coating. In addition, the nano silica in the composite filler can scatter and reflect ultraviolet rays, and the hydrotalcite can delay the propagation path of ultraviolet rays through physical barrier. The conjugated double bonds and phenolic hydroxyl groups in the quercetin molecule can absorb ultraviolet rays, preventing ultraviolet rays from directly irradiating the polyurethane molecular chain and reducing the photo-oxidative degradation of the molecular chain. Therefore, quercetin and composite filler can also synergistically improve the UV aging resistance of the coating. Attached Figure Description

[0035] Figure 1 This is a flowchart illustrating the preparation process of the waterproof polyurethane composite coating used in an embodiment of the present invention. Detailed Implementation

[0036] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of this invention.

[0037] Example 1: A preparation process for a waterproof polyurethane composite coating, as follows... Figure 1 As shown, it includes the following steps:

[0038] S1: Preparation of quercetin-grafted composite filler

[0039] S1.1: The nanosilica was added into deionized water at 1 g:40 mL, and ultrasonic dispersion was carried out for 30 min to obtain a nanosilica dispersion;

[0040] S1.2: The magnesium nitrate hexahydrate and aluminum nitrate nonahydrate were added into deionized water at 1.7 g:1 g:10 mL, and after being fully stirred and dissolved, the above-mentioned nanosilica dispersion was added, and after being stirred and mixed, a mixed alkali solution was added at 2 mL / min, the pH was adjusted to 9, and stirring was continued for 1 h to obtain a precursor solution, wherein the mass ratio of nanosilica to magnesium nitrate hexahydrate was 1:8, and the mixed alkali solution was prepared by dissolving sodium hydroxide and sodium carbonate in deionized water at a solid-liquid ratio of 3.8 g:1 g:45 mL;

[0041] S1.3: The above-mentioned precursor solution was transferred to a high-pressure reaction kettle, and crystallization was carried out at 75℃ for 10 h, and after being naturally cooled to room temperature, centrifugal separation, washing to neutral, vacuum drying and grinding were carried out to obtain a composite filler;

[0042] S1.4: The 3-aminopropyl triethoxysilane was added into a 90% volume fraction ethanol solution at 1 g:100 mL, and glacial acetic acid was added to adjust the pH to 4, and after being stirred and hydrolyzed for 20 min, the above-mentioned composite filler was added at 1 g:10 mL, and after being heated and stirred at 50℃ for 4 h, after being cooled, centrifugal separation, washing and vacuum drying were carried out to obtain an aminated composite filler;

[0043] S1.5: The quercetin, p-toluenesulfonic acid and hydroquinone were added into anhydrous ethanol at 0.8 g:0.05 g:0.01 g:90 mL, and after being heated and stirred to dissolve at 50℃, the above-mentioned aminated composite filler was added at 1 g:20 mL, and after being heated and stirred to reflux at 70℃ for 5 h under nitrogen protection, after being cooled, centrifugal separation, washing and vacuum drying were carried out to obtain a quercetin grafted composite filler;

[0044] S2: Preparation of modified isophorone diisocyanate solution

[0045] S2.1: The 3,5-di-tert-butyl-4-hydroxybenzoic acid was added into anhydrous acetone at 1 g:10 mL, and after being heated and stirred to dissolve at 50℃, a 3,5-di-tert-butyl-4-hydroxybenzoic acid solution was obtained;

[0046] S2.2: When the temperature of the above 3,5-di-tert-butyl-4-hydroxybenzoic acid solution is reduced to 40℃, 2,6-di-tert-butyl-p-cresol and dibutyltin dilaurate are added, the mixture is stirred, then isophorone diisocyanate is added at a rate of 3mL / min, and the reaction is heated at 60℃ for 2.5h under nitrogen protection to obtain a modified isophorone diisocyanate solution, wherein the amount of dibutyltin dilaurate added is 0.3% of the mass of 3,5-di-tert-butyl-4-hydroxybenzoic acid, the amounts of 2,6-di-tert-butyl-p-cresol and dibutyltin dilaurate are equal, and the molar ratio of isophorone diisocyanate to 3,5-di-tert-butyl-4-hydroxybenzoic acid is 2:1;

[0047] S3: Preparation of polyurethane composite coating

[0048] S3.1: Polybutylene adipate, dimethylol butanoic acid and dibutyltin dilaurate are added to the above modified isophorone diisocyanate solution, and the reaction is heated and stirred at 65℃ for 3h to obtain a prepolymer;

[0049] S3.2: 2-hydroxy-5-substituted long-chain fatty acyloxybenzoic acid methyl ester is added to the above prepolymer, and the reaction is heated and stirred for 2h, then trimethylolpropane is added and the reaction is continued for 2h to obtain a precursor solution;

[0050] S3.3: 1,4-butanediol is added to the above precursor solution, and the reaction is continued to stir for 1h, then triethylamine and acetone are added when the temperature is reduced to 35℃, the mixture is stirred, then the above quercetin grafted composite filler is added, the mixture is fully mixed and uniform, then water is added for emulsification to obtain a polyurethane composite coating, wherein the raw material composition of the polyurethane composite coating is 90 parts of polybutylene adipate, 70 parts of modified isophorone diisocyanate solution, 10 parts of quercetin grafted composite filler, 9 parts of dimethylol butanoic acid, 7 parts of 2-hydroxy-5-substituted long-chain fatty acyloxybenzoic acid methyl ester, 5 parts of trimethylolpropane, 3 parts of 1,4-butanediol, 0.06 parts of dibutyltin dilaurate, 1.4 parts of triethylamine, 20 parts of acetone and 50 parts of water.

[0051] Example 2, a preparation process of a waterproof polyurethane composite coating, as shown in Figure 1 , comprising the following steps:

[0052] S1: Preparation of quercetin grafted composite filler

[0053] S1.1: Nano-silicon dioxide is added to deionized water at a ratio of 1g:45mL, and ultrasonic dispersion is performed for 35min to obtain a nano-silicon dioxide dispersion;

[0054] S1.2: Add magnesium nitrate hexahydrate and aluminum nitrate nonahydrate into deionized water according to 1.75 g: 1 g: 13 mL, after fully stirring and dissolving, add the above nano-silica dispersion solution, stir and mix, then add mixed alkali solution at 3 mL / min, adjust pH to 9.5, and continue stirring for 1.5 h to obtain a precursor solution, wherein the mass ratio of nano-silica to magnesium nitrate hexahydrate is 1:9, and the mixed alkali solution is prepared by dissolving sodium hydroxide and sodium carbonate in deionized water according to solid-liquid ratio of 3.9 g: 1 g: 47 mL;

[0055] S1.3: Transfer the above precursor solution into a high-pressure reaction kettle, crystallize at 80℃ for 11 h, naturally cool to room temperature, then separate by centrifugation, wash to neutral, vacuum dry and grind to obtain a composite filler;

[0056] S1.4: Add 3-aminopropyl triethoxysilane into a 90% volume fraction ethanol solution according to 1 g: 150 mL, and add glacial acetic acid to adjust pH to 4.5, stir and hydrolyze for 25 min, then add the above composite filler according to 1 g: 15 mL, heat and stir at 55℃ for 4.5 h, then after cooling, separate by centrifugation, wash and vacuum dry to obtain an aminated composite filler;

[0057] S1.5: Add quercetin, p-toluenesulfonic acid and hydroquinone into anhydrous ethanol according to 0.9 g: 0.08 g: 0.01 g: 95 mL, heat and stir to dissolve at 55℃, then add the above aminated composite filler according to 1 g: 25 mL, and heat and stir to reflux at 75℃ for 5.5 h under nitrogen protection, then after cooling, separate by centrifugation, wash and vacuum dry to obtain a quercetin grafted composite filler;

[0058] S2: Preparation of modified isophorone diisocyanate solution

[0059] S2.1: Add 3,5-di-tert-butyl-4-hydroxybenzoic acid into anhydrous acetone according to 1 g: 15 mL, heat and stir to dissolve at 55℃ to obtain a 3,5-di-tert-butyl-4-hydroxybenzoic acid solution;

[0060] S2.2: When the temperature of the above 3,5-di-tert-butyl-4-hydroxybenzoic acid solution is reduced to 40℃, add 2,6-di-tert-butyl-p-cresol and dibutyltin dilaurate, stir and mix, then add isophorone diisocyanate at 4 mL / min, and heat to react at 63℃ for 3 h under nitrogen protection to obtain a modified isophorone diisocyanate solution, wherein the amount of dibutyltin dilaurate added is 0.35% of the mass of 3,5-di-tert-butyl-4-hydroxybenzoic acid, the amounts of 2,6-di-tert-butyl-p-cresol and dibutyltin dilaurate are equal, and the molar ratio of isophorone diisocyanate to 3,5-di-tert-butyl-4-hydroxybenzoic acid is 2:1;

[0061] S3: Preparation of polyurethane composite coating

[0062] S3.1: The polybutylene adipate, dimethylol butyric acid and dibutyltin dilaurate are added to the modified isophorone diisocyanate solution described above, heated and stirred at 68℃ for 3.5h to obtain a prepolymer;

[0063] S3.2: The 2-hydroxy-5-substituted long-chain fatty acyloxy methyl benzoate is added to the prepolymer described above, and the reaction is stirred and incubated for 2.5h. Then trimethylolpropane is added and the reaction is continued for another 2.5h to obtain a precursor solution;

[0064] S3.3: The 1,4-butanediol is added to the precursor solution described above, and the reaction is continued to stir for 1.5h. When the temperature is reduced to 35℃, the triethylamine and acetone are added, and after stirring and mixing, the quercetin grafted composite filler described above is added, and after fully mixing and uniformity, water is added for emulsification to obtain a polyurethane composite coating. The raw material composition of the polyurethane composite coating is as follows in terms of mass fraction: 95 parts of polybutylene adipate, 75 parts of modified isophorone diisocyanate solution, 11 parts of quercetin grafted composite filler, 10 parts of dimethylol butyric acid, 8 parts of 2-hydroxy-5-substituted long-chain fatty acyloxy methyl benzoate, 5.5 parts of trimethylolpropane, 4 parts of 1,4-butanediol, 0.08 parts of dibutyltin dilaurate, 1.6 parts of triethylamine, 25 parts of acetone and 55 parts of water.

[0065] Example 3, a preparation process of a waterproof polyurethane composite coating, as shown in Figure 1 , includes the following steps:

[0066] S1: Preparation of quercetin grafted composite filler

[0067] S1.1: The nanosilica is added to deionized water at a ratio of 1g:50mL, and ultrasonic dispersion is performed for 40min to obtain a nanosilica dispersion;

[0068] S1.2: The magnesium nitrate hexahydrate and aluminum nitrate nonahydrate are added to deionized water at a ratio of 1.8g:1g:16mL, and after fully stirring and dissolving, the nanosilica dispersion described above is added, and after stirring and mixing, the mixed alkali solution is added at a rate of 4mL / min to adjust the pH to 10, and the stirring is continued for 2h to obtain a precursor solution. The mass ratio of nanosilica to magnesium nitrate hexahydrate is 1:10, and the mixed alkali solution is prepared by dissolving sodium hydroxide and sodium carbonate in deionized water at a solid-liquid ratio of 4g:1g:50mL;

[0069] S1.3: The precursor solution described above is transferred to a high-pressure reaction kettle, and crystallization is performed at 85℃ for 12h. After natural cooling to room temperature, centrifugal separation, washing to neutral, vacuum drying and grinding are performed to obtain a composite filler;

[0070] S1.4: 3-aminopropyltriethoxysilane was added into a 90% volume fraction ethanol solution at 1 g:200 mL, and glacial acetic acid was added to adjust the pH to 5, stirred and hydrolyzed for 30 min, then the above-mentioned composite filler was added at 1 g:20 mL, heated and stirred at 60°C for 5 h, after cooling, centrifugal separation, washing and vacuum drying, the aminated composite filler was obtained;

[0071] S1.5: quercetin, p-toluenesulfonic acid and hydroquinone were added into anhydrous ethanol at 1 g:0.1 g:0.01 g:100 mL, after heated and stirred to dissolve at 60°C, the above-mentioned aminated composite filler was added at 1 g:30 mL, and heated and stirred to reflux at 80°C for 6 h under nitrogen protection, after cooling, centrifugal separation, washing and vacuum drying, the quercetin grafted composite filler was obtained;

[0072] S2: preparation of modified isophorone diisocyanate solution

[0073] S2.1: 3,5-di-tert-butyl-4-hydroxybenzoic acid was added into anhydrous acetone at 1 g:20 mL, heated and stirred to dissolve at 60°C, and the 3,5-di-tert-butyl-4-hydroxybenzoic acid solution was obtained;

[0074] S2.2: when the above-mentioned 3,5-di-tert-butyl-4-hydroxybenzoic acid solution was cooled to 40°C, 2,6-di-tert-butyl-p-cresol and dibutyltin dilaurate were added, stirred and mixed, then isophorone diisocyanate was added at 5 mL / min, and reacted at 65°C for 3.5 h under nitrogen protection, to obtain the modified isophorone diisocyanate solution, wherein the amount of dibutyltin dilaurate added was 0.4% of the mass of 3,5-di-tert-butyl-4-hydroxybenzoic acid, the amount of 2,6-di-tert-butyl-p-cresol and dibutyltin dilaurate was equal, and the molar ratio of isophorone diisocyanate to 3,5-di-tert-butyl-4-hydroxybenzoic acid was 2:1;

[0075] S3: preparation of polyurethane composite coating

[0076] S3.1: polybutylene glycol adipate, dimethylol butyric acid and dibutyltin dilaurate were added into the above-mentioned modified isophorone diisocyanate solution, and reacted at 70°C for 4 h to obtain a prepolymer;

[0077] S3.2: 2-hydroxy-5-substituted long-chain fatty acyloxybenzoic acid methyl ester was added to the above-mentioned prepolymer, and reacted for 3 h under heat and stirring, then trimethylolpropane was added, and reacted for another 3 h to obtain a precursor solution;

[0078] S3.3: 1,4-butanediol was added to the above precursor solution, and the reaction was continued to stir for 2 h. When the temperature was lowered to 35℃, triethylamine and acetone were added. After stirring the mixture, the above quercetin grafted composite filler was added, and after fully mixing and uniformity, water was added for emulsification to obtain a polyurethane composite coating. The raw material composition of the polyurethane composite coating was as follows: 100 parts of polybutylene glycol adipate, 80 parts of modified isophorone diisocyanate solution, 12 parts of quercetin grafted composite filler, 11 parts of dimethylol butyric acid, 9 parts of 2-hydroxy-5-substituted long-chain fatty acyl oxybenzoic acid methyl ester, 6 parts of trimethylolpropane, 5 parts of 1,4-butanediol, 0.1 parts of dibutyltin dilaurate, 1.8 parts of triethylamine, 30 parts of acetone and 60 parts of water.

[0079] Comparative Example 1, the difference between Comparative Example 1 and Example 1 is that the 2-hydroxy-5-substituted long-chain fatty acyl oxybenzoic acid methyl ester in step S4 is replaced with an equal amount of ethylenediamine.

[0080] Comparative Example 2, the difference between Comparative Example 2 and Example 1 is that step S2 is removed, and the modified isophorone diisocyanate solution in step S3 is replaced with an equal amount of isophorone diisocyanate-acetone solution, wherein the mass of isophorone diisocyanate in the isophorone diisocyanate-acetone solution is equal to that of the modified isophorone diisocyanate in the modified isophorone diisocyanate solution.

[0081] Comparative Example 3, the difference between Comparative Example 3 and Example 1 is that the quercetin grafted composite filler in step S3 is replaced with quercetin and aminated composite filler, wherein the amount of quercetin added is equal to the content of quercetin in the quercetin grafted composite filler in Example 1, and the amount of composite filler added is equal to the content of composite filler in the quercetin grafted composite filler in Example 1.

[0082] Comparative Example 4, the difference between Comparative Example 4 and Example 1 is that the quercetin grafted composite filler in step S3 is replaced with an equal amount of aminated composite filler.

[0083] Comparative Example 5, the difference between Comparative Example 5 and Example 1 is that the quercetin grafted composite filler in step S3 is replaced with an equal amount of quercetin.

[0084] Test Example:

[0085] Test 1: The polyurethane composite coatings prepared in Examples 1-3 and Comparative Example 1 were made into coatings, and the water resistance was tested according to GB / T1733-1993, and the adhesion was tested according to GB / T9286-2021, and the results are shown in Table 1.

[0086] Table 1: Water resistance and adhesion test results of polyurethane composite coatings

[0087]

[0088] From the above table 1, in the comparative example 1, the 2-hydroxy-5-substituted long chain fatty acyl oxybenzoic acid methyl ester is replaced by an equal amount of ethylenediamine, the adhesion grade of the coating layer formed by the prepared polyurethane composite coating is 1, which is lower than that of example 1, and after 720h water resistance test, bubbling and peeling occur, while the coating layer prepared in example 1 does not bubble and peel, thus it can be seen that by mixing polybutylene adipate, dimethylol butyric acid and dibutyl tin dilaurate with modified isophorone diisocyanate solution to carry out pre-polymerization, then adding 2-hydroxy-5-substituted long chain fatty acyl oxybenzoic acid methyl ester for reaction, introducing long chain fatty acyl and methyl benzoate structure into the polyurethane molecular chain, adding trimethylolpropane for crosslinking reaction to increase the crosslinking degree of the molecular chain, and finally adding 1,4-butanediol as a chain extender to react with the remaining -NCO, after neutralization with triethylamine, viscosity reduction with acetone and emulsification with water, the polyurethane composite coating can effectively improve the water resistance and adhesion of the polyurethane composite coating.

[0089] Test 2: After the polyurethane composite coating prepared in examples 1-3 and comparative example 2 is made into a coating layer, its heat aging and water resistance test is carried out, and the results are shown in table 2.

[0090] Table 2: Test results of heat aging and water resistance performance of polyurethane composite coating

[0091]

[0092] From the above table 2, in the comparative example 2, after grafting modification of 3,5-di-tert-butyl-4-hydroxybenzoic acid on isophorone diisocyanate, the coating layer prepared is cracked after baking at 200℃ for 72h, and bubbling occurs after 720h water resistance test, thus it can be seen that after dissolving 3,5-di-tert-butyl-4-hydroxybenzoic acid, adding isophorone diisocyanate for reaction under the catalysis of dibutyl tin dilaurate, introducing 3,5-di-tert-butyl-4-hydroxybenzoic acid into isophorone diisocyanate molecule to prepare modified isophorone diisocyanate, the polyurethane composite coating prepared from the modified isophorone diisocyanate and polybutylene adipate can improve its heat aging performance and water resistance.

[0093] Test 3: After the polyurethane composite coating prepared in examples 1-3 and comparative examples 3-4 is made into a coating layer, the coating layer is subjected to aging test in a ultraviolet aging test box with ultraviolet wavelength of 330nm, radiation intensity of 50W / cm 2 , and temperature of 48℃ for 168h, and the results are shown in table 3.

[0094] Table 3: Test results of ultraviolet aging resistance performance of polyurethane composite coating

[0095]

[0096] From Table 3, it can be seen that, after the quercetin and the aminated composite filler were directly added into the coating in Comparative Example 3, the coating layer formed by the prepared polyurethane composite coating appeared cracking after ultraviolet aging for 168 h, indicating that, after the quercetin was grafted on the surface of the composite filler, the quercetin could be uniformly dispersed in the coating matrix with the composite filler carrier, and the quercetin could inhibit the migration of the quercetin in the coating matrix after being grafted on the surface of the composite filler by chemical bonding, thereby effectively improving the long-term ultraviolet aging resistance of the coating. In addition, when only the single aminated composite filler was added in Comparative Example 4, the coating layer formed by the prepared polyurethane composite coating appeared cracking after ultraviolet aging for 168 h, and when only the single quercetin was added in Comparative Example 5, the coating layer formed by the prepared polyurethane composite coating appeared cracking and peeling after ultraviolet aging for 168 h, indicating that the quercetin and the composite filler could synergistically improve the ultraviolet aging resistance of the coating.

[0097] It should be understood that, for those skilled in the art, improvements or changes can be made according to the above description, and all these improvements and changes shall belong to the protection scope of the appended claims of the present application. The parts not described in detail in the specification belong to the prior art known to those skilled in the art.

Claims

1. A process for the preparation of a water-proof polyurethane composite coating, characterized in that, Comprising the following steps: S1: preparing quercetin grafted composite filler S1.1: adding nano-silica into deionized water at 1g:(40-50)mL, ultrasonic dispersion for 30-40min to obtain nano-silica dispersion; S1.2: adding magnesium nitrate hexahydrate and aluminum nitrate nonahydrate into deionized water at (1.7-1.8)g:1g:(10-16)mL, after fully stirring and dissolving, adding the above nano-silica dispersion, after stirring and mixing, adding mixed alkali solution at 2-4mL / min, adjusting pH to 9-10, and continuing to stir for 1-2h to obtain a precursor solution; S1.3: transferring the above precursor solution into a high-pressure reaction kettle, crystallizing at 75-85℃ for 10-12h, naturally cooling to room temperature, then centrifuging, washing to neutral, vacuum drying and grinding to obtain a composite filler; S1.4: adding 3-aminopropyl triethoxysilane into a 90% volume fraction ethanol solution at 1g:(100-200)mL, and adding glacial acetic acid to adjust pH to 4-5, stirring and hydrolyzing for 20-30min, then adding the above composite filler at 1g:(10-20)mL, heating and stirring at 50-60℃ for 4-5h, after cooling, centrifuging, washing and vacuum drying to obtain an aminated composite filler; S1.5: adding quercetin, p-toluenesulfonic acid and hydroquinone into anhydrous ethanol at (0.8-1)g:(0.05-0.1)g:0.01g:(90-100)mL, after heating and stirring to dissolve at 50-60℃, adding the above aminated composite filler at 1g:(20-30)mL, and heating and stirring under reflux at 70-80℃ for 5-6h under nitrogen protection, after cooling, centrifuging, washing and vacuum drying to obtain a quercetin grafted composite filler; S2: preparing modified isophorone diisocyanate solution After dissolving 3,5-di-tert-butyl-4-hydroxybenzoic acid, adding isophorone diisocyanate to react to obtain a modified isophorone diisocyanate solution; S3: preparing polyurethane composite coating S3.1: adding polybutylene glycol adipate, dimethylol butanoic acid and dibutyltin dilaurate into the above modified isophorone diisocyanate solution, heating and stirring to react at 65-70℃ for 3-4h to obtain a prepolymer; S3.2: adding 2-hydroxy-5-substituted long-chain fatty acyl oxybenzoic acid methyl ester into the above prepolymer, heating and stirring to react for 2-3h, then adding trimethylolpropane to continue to react for 2-3h to obtain a precursor solution; S3.3: adding 1,4-butanediol into the above precursor solution to continue to stir for 1-2h, after cooling to 35℃, adding triethylamine and acetone, stirring and mixing, then adding the above quercetin grafted composite filler, fully mixing uniformly, then adding water to emulsify to obtain a polyurethane composite coating.

2. The process for preparing a waterproof polyurethane composite coating according to claim 1, characterized in that, S2 specifically comprises the following steps: S2.1: 3,5-di-tert-butyl-4-hydroxybenzoic acid is added into anhydrous acetone at 1 g: (10-20) mL, and dissolved by heating and stirring at 50-60℃ to obtain a 3,5-di-tert-butyl-4-hydroxybenzoic acid solution; S2.2: After the temperature of the above 3,5-di-tert-butyl-4-hydroxybenzoic acid solution is reduced to 40℃, 2,6-di-tert-butyl-p-cresol and dibutyltin dilaurate are added, and after stirring and mixing, isophorone diisocyanate is added at 3-5 mL / min, and the reaction is carried out under nitrogen protection at 60-65℃ for 2.5-3.5 h to obtain a modified isophorone diisocyanate solution.

3. The process for preparing a water-proof polyurethane composite coating according to claim 1, characterized in that, The mass ratio of nano-silicon dioxide to magnesium nitrate hexahydrate is 1: (8-10).

4. The process for preparing a water-proof polyurethane composite coating according to claim 1, characterized in that, The mixed alkali solution is prepared by dissolving sodium hydroxide and sodium carbonate in deionized water at a solid-liquid ratio of (3.8-4) g: 1 g: (45-50) mL.

5. The process for preparing a water-proof polyurethane composite coating according to claim 2, characterized in that, The amount of dibutyltin dilaurate added is 0.3-0.4% of the mass of 3,5-di-tert-butyl-4-hydroxybenzoic acid.

6. The process for preparing a water-proof polyurethane composite coating according to claim 2, characterized in that, The amount of 2,6-di-tert-butyl-p-cresol and dibutyltin dilaurate added is equal.

7. The process for preparing a water-proof polyurethane composite coating according to claim 2, characterized in that, The molar ratio of isophorone diisocyanate to 3,5-di-tert-butyl-4-hydroxybenzoic acid is 2:

1.

8. The process for preparing a water-proof polyurethane composite coating according to claim 1, characterized in that, The raw material composition of the polyurethane composite coating is 90-100 parts of polybutylene adipate, 70-80 parts of modified isophorone diisocyanate solution, 10-12 parts of quercetin grafted composite filler, 9-11 parts of dimethylol butyric acid, 7-9 parts of 2-hydroxy-5-substituted long-chain fatty acyloxybenzoic acid methyl ester, 5-6 parts of trimethylolpropane, 3-5 parts of 1,4-butanediol, 0.06-0.1 parts of dibutyltin dilaurate, 1.4-1.8 parts of triethylamine, 20-30 parts of acetone, and 50-60 parts of water.

9. A water repellent polyurethane composite coating characterized by, It is prepared by the preparation process of a waterproof polyurethane composite coating according to any one of claims 1-8. It is prepared by the preparation process of a waterproof polyurethane composite coating according to any one of claims 1-8.

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