A waterproof bio-based polyurethane coating and a preparation process thereof

Abstract

The application relates to the polyurethane coating processing field, in particular to a waterproof bio-based polyurethane coating and a preparation process thereof, which is prepared from the following raw materials in percentage by weight: castor oil polyester polyol 25-40%, isocyanate 15-25%, bio-based polyacid 5-10%, catalyst 0.2-0.6%, chain extender 0.5-1%, modified nano filler 15-20%, wetting agent 3-5%, curing agent 1-2%, and the rest is solvent. Through the above formula, the waterproof bio-based polyurethane coating prepared has good weather resistance, high and low temperature resistance, strength and waterproofness, can be used for a long time in the northwest region without aging, and the service life of the waterproof coating is prolonged.

Description

Technical Field

[0001] This application relates to the field of polyurethane coating processing, and more specifically, to a waterproof bio-based polyurethane coating and its preparation process. Background Technology

[0002] Bio-based polyurethane coatings are green, environmentally friendly, non-toxic, odorless, and pollution-free coatings commonly used in the construction industry, especially for roof waterproofing. By applying bio-based polyurethane coatings to the roof, a continuous and dense waterproof membrane is formed, effectively preventing water penetration and protecting the roof structure from water damage.

[0003] In roof waterproofing, bio-based polyurethane coatings can be evenly and tightly applied to the roof surface to form a continuous and dense waterproof membrane. This not only effectively prevents rainwater penetration and damages the roof structure due to long-term immersion, but also resists some common chemical corrosion and physical wear, extending the service life of the building.

[0004] However, in Northwest my country, the extreme natural environmental conditions, such as long hours of sunshine in summer, high solar radiation intensity, and significant temperature differences between summer and winter, pose even more stringent challenges to the use of bio-based polyurethane coatings. Prolonged intense sunlight in the Northwest accelerates the oxidation process of the coating, easily causing the molecular chains of the bio-based polyurethane coating to break, leading to aging, discoloration, and even chalking. Simultaneously, significant temperature changes subject the coating material to cyclic stress from thermal expansion and contraction, making it prone to the appearance and gradual expansion of micro-cracks, ultimately affecting the overall waterproofing effect and durability of the coating, resulting in a shorter service life. Summary of the Invention

[0005] To address the issue of short service life of bio-based polyurethane coatings in Northwest China, this application provides a waterproof bio-based polyurethane coating and its preparation process.

[0006] In a first aspect, this application provides a waterproof bio-based polyurethane coating, employing the following technical solution: A waterproof bio-based polyurethane coating is prepared from the following raw materials in weight percentages: Castor oil polyester polyols 25-40% Isocyanates 15-25% Bio-based polyacids 5-10% Catalyst 0.2-0.6% Chain extender 0.5-1% Modified nanofillers 15-20% wetting agent 3-5% 1-2% of curing agent The remainder is diluent.

[0007] By adopting the above technical solution, the prepared waterproof bio-based polyurethane coating has good weather resistance, high and low temperature resistance, strength and waterproofness. It can be used for a long time in the Northwest region without aging, thus extending the service life of the waterproof coating.

[0008] In this process, isocyanate undergoes a cross-linking reaction with castor oil polyester polyol and bio-based polyacids to form a three-dimensional network structure of polyurethane. This slows down the aging process of the coating under prolonged exposure to strong sunlight, reducing discoloration and chalking. The optimal ratio of isocyanate to chain extender ensures a high-strength and stable cross-linked structure after curing, effectively resisting thermal expansion and contraction stress caused by significant temperature changes, reducing the formation of micro-cracks, and maintaining the integrity and waterproof performance of the coating. The cross-linking reaction of the bio-based polyacid coating enhances the rigidity and toughness of the polyurethane molecular chains, making the coating more resistant to aging, discoloration, and chalking in extreme environments, maintaining its long-lasting appearance and performance. Modified nanofillers improve the UV resistance, aging resistance, and mechanical strength of waterproof bio-based polyurethane coatings because: the small size and surface effects of the modified nanofillers effectively block UV penetration, slowing down the oxidation process of the coating; simultaneously, their high specific surface area provides more cross-linking points, enhancing the density and durability of the coating. The formula includes appropriate amounts of wetting agents and thinners to improve the wettability and flowability of the coating, making the application process smoother and enabling the formation of a uniform, defect-free coating. The curing agent further promotes the cross-linking and curing of the coating, resulting in a higher hardness and better chemical resistance after curing.

[0009] Preferably, the modified nanofiller is prepared by the following method: 1) Dry the nanofiller, then place it in ethanol and ultrasonically disperse it to obtain a turbid liquid; 2) Stir the turbid liquid, 3-aminopropyltriethoxysilane and benzotriazole at 50-70℃ for 1-2 hours to obtain mixture 1; 3) Dissolve isocyanate and organosilicon diol in ethanol to obtain mixture 2; 4) Mixture 1 and mixture 2 are stirred and reacted at 60-70℃ for 1-2 hours, filtered, and the filter residue is collected to obtain the modified nanofiller.

[0010] Preferably, the raw materials used to prepare the modified nanofiller are in the following weight proportions: 30-40 parts of nanofiller 5-8 parts of 3-aminopropyltriethoxysilane 1-3 parts of benzotriazole 10-13 parts isocyanate 8-10 parts of organosilicon diol 25-35 parts ethanol.

[0011] By adopting the above technical solution, the modified nanofiller can be uniformly dispersed in the waterproof bio-based polyurethane coating system, further improving the UV resistance, aging resistance and strength of the waterproof bio-based polyurethane coating, and extending the service life of the coating after curing.

[0012] In step 1), ultrasonic treatment ensures uniform nano-level dispersion of the nanofiller particles in ethanol, providing favorable conditions for subsequent reactions. In step 2), 3-aminopropyltriethoxysilane forms an organosilicon layer on the surface of the nanofiller, improving the compatibility and interfacial bonding between the nanofiller and the polyurethane matrix. Benzotriazole, acting as an anti-aging agent, imparts better UV resistance and antioxidant properties to the nanofiller, thus protecting the entire coating system. In step 3), the reaction of isocyanate with organosilicon diol in ethanol, followed by further reaction with mixture 1, successfully introduces isocyanate groups onto the surface of the nanofiller. This allows the modified nanofiller to chemically react with the polyester polyol in the polyurethane coating, forming strong chemical bonds, enhancing the stability and dispersibility of the nanofiller in the coating, thereby improving the UV resistance, aging resistance, and strength of the waterproof bio-based polyurethane coating.

[0013] Preferably, the average particle size of the nanofiller is 20-300 nm.

[0014] By adopting the above technical solution, the particle size of the nanofiller is optimized and the specific surface area of ​​the nanofiller is increased, which greatly increases the contact area between the nanofiller and the polyurethane matrix. This enhances the interfacial interaction and bonding force, helps the nanofiller to be dispersed more stably in the coating, and more effectively transfers stress, thereby improving the overall performance of the coating.

[0015] Preferably, the diluent is obtained by mixing ethanol and an ester solvent in a weight ratio of (7-8):10, wherein the ester solvent is one of ethyl acetate, butyl acetate, or dimethyl carbonate.

[0016] By adopting the above technical solutions, the type of diluent is optimized, and the viscosity of the waterproof bio-based polyurethane coating is adjusted, making it easier to apply and level during construction. Simultaneously, ethanol and ester solvents both possess good volatility and solubility, ensuring that the coating is quickly and evenly applied to the substrate surface and dries rapidly to form a film. Ethanol and ester solvents (ethyl acetate, butyl acetate, or dimethyl carbonate) are all environmentally friendly solvents with low toxicity and volatile organic compound (VOC) emissions, meeting the environmental performance requirements of the modern coatings industry and helping to reduce harm to the environment and human health during coating use.

[0017] Preferably, the castor oil polyester polyol has a hydroxyl value of 85-150 mgKOH / g and a functionality of 1-3.

[0018] By employing the above technical solutions, the hydroxyl value and functionality of castor oil are optimized, and the reactivity of castor oil polyols is improved. This allows the coating to form a dense cross-linked network during the curing process, thereby enhancing its waterproof performance. Simultaneously, it helps strengthen the coating's cohesion and adhesion, enabling it to better adhere to the substrate surface and form a continuous waterproof layer. Preferably, the bio-based polyacid is one of furanyl dicarboxylic acid, palmitic acid, oleic acid, malic acid, and citric acid.

[0019] By adopting the above technical solutions, the types of bio-based polyacids are optimized, further promoting the cross-linking reaction of the coating, enhancing the rigidity and toughness of the polyurethane molecular chains, and making the coating more resistant to aging, discoloration and chalking in extreme environments, thus maintaining a long-lasting appearance and performance.

[0020] Preferably, the chain extender is obtained by mixing diethyltoluenediamine and ethanolamine in a weight ratio of (3-4):1.

[0021] By employing the above technical solution, diethyltoluenediamine and ethanolamine jointly promote the crosslinking reaction of polyurethane coatings, increasing the crosslinking density and strength of the coatings, and also improving the flexibility and low-temperature resistance of the coatings. Specifically, the isocyanate groups of diethyltoluenediamine react to form urea bond crosslinking structures, improving the cohesiveness and strength of the polyurethane coatings, thus giving them better abrasion resistance, tear resistance, and chemical resistance. Ethanolamine forms hydrogen bonds with other groups in the polyurethane molecular chain through hydroxyl groups, thereby enhancing the intermolecular interaction forces and improving the low-temperature resistance of the coatings, allowing the coatings to maintain good physical properties even at low temperatures.

[0022] Preferably, the wetting agent is obtained by mixing nonylphenol polyoxyethylene ether and polyoxyethylene fatty alcohol ether in a weight ratio of (5-6):3.

[0023] By adopting the above technical solutions, the wettability and spreadability of waterproof bio-based polyurethane coatings are improved, making them easier to apply to roof substrates. Simultaneously, the fluidity and leveling properties of the waterproof bio-based polyurethane coatings are enhanced, reducing defects such as bubbles and pinholes during application, and improving the gloss and smoothness of the coating.

[0024] Secondly, this application provides a preparation process for a waterproof bio-based polyurethane coating, employing the following technical solution: A process for preparing a waterproof bio-based polyurethane coating includes the following preparation steps: S1. Under dry nitrogen protection, castor oil polyol is added to the reaction vessel, heated to 110-120℃ and dehydrated under reduced pressure, and then the system temperature is reduced to 60-80℃. S2. Add bio-based polyacid, isocyanate and catalyst to the reaction vessel, mix well, adjust the viscosity of the mixture with solvent, and maintain the reaction at 60-80℃ for 7-9 hours. After the reaction in step S2 is completed, a chain extender is added to carry out a crosslinking reaction. The mixture is stirred, and then modified nanofillers, wetting agents, and curing agents are added and stirred to obtain a bio-based polyurethane coating.

[0025] The bio-based polyurethane coating prepared by the above process has excellent waterproof, weather-resistant, high and low temperature resistant and anti-aging properties. It can maintain stable performance under extreme natural environmental conditions, effectively prevent water penetration and protect the roof structure from water damage.

[0026] In summary, this application has the following beneficial effects: 1. Enhanced weather resistance and anti-aging properties: Castor oil polyester polyol, as one of the main components of the formula, not only meets environmental protection requirements due to its bio-based properties, but also effectively resists oxidative degradation under prolonged exposure to strong sunlight due to its excellent UV resistance. The addition of bio-based polyacids further enhances the molecular stability of the coating, slows down the aging process caused by light exposure, and ensures that the coating maintains excellent appearance and performance even under extreme sunlight conditions.

[0027] 2. Excellent high and low temperature resistance: By precisely controlling the ratio of isocyanate to chain extender in the formulation, a highly cross-linked polyurethane structure is formed. This structure can better resist the stress of thermal expansion and contraction when subjected to large temperature changes, reducing the generation and propagation of microcracks. The addition of modified nanofillers further enhances the microstructural strength of the coating, strengthens its resistance to temperature cycling, and maintains the integrity and waterproof performance of the coating.

[0028] 3. Excellent waterproof performance: This coating can be evenly and tightly applied to the roof surface, forming a continuous and dense waterproof membrane that effectively prevents the penetration of rainwater and other liquids. Simultaneously, its excellent chemical stability resists common chemical corrosion, such as acid rain and salt spray, protecting the roof structure from damage. Furthermore, the coating's physical abrasion resistance is also improved, resisting physical wear from natural factors such as wind and sand, extending its service life. Detailed Implementation Example

[0029] Example 1 A waterproof bio-based polyurethane coating is prepared by the following method: S1. Under dry nitrogen protection, 250g of castor oil polyol was added to the reaction vessel, heated to 110℃ and dehydrated under reduced pressure for 1 hour, and then the system temperature was lowered to 60℃. S2. Add 250g of bio-based polybasic acid (furan dicarboxylic acid), 50g of isocyanate (hexamethylene diisocyanate), and 2g of catalyst (dibutyltin dilaurate) to the reaction vessel. After mixing evenly, adjust the viscosity of the mixture with 203g of diluent (ethanol) and maintain the reaction at 60°C for 7 hours. After the reaction in step S2 is completed, add 5g of chain extender (diethyltoluene diamine) to carry out the crosslinking reaction, stir, then add 200g of modified nanofiller (modified nano silica), 30g of wetting agent (nonylphenol polyoxyethylene ether), and 10g of curing agent (trimethylolpropane tris(3-propyleneimine)propionate) and stir to obtain a bio-based polyurethane coating.

[0030] The modified nano-silica was purchased from Shanghai Zhenlishi Network Technology Co., Ltd., model number M5.

[0031] The difference between Examples 2-3 and Example 1 lies in the types and amounts of some raw materials used in the preparation of the bio-based polyurethane coating, as well as the experimental parameters. Specific differences are shown in Table 1. Table 1. Types, dosages, and experimental parameters of raw materials used in the preparation of bio-based polyurethane coatings in Examples 1-3.

[0032] Example 4 A waterproof bio-based polyurethane coating, the difference between this embodiment and Example 1 is that the modified nanofiller is prepared by the following method: 1) Dry 300g of nanofiller (nano silica, with an average particle size of 20-50nm), and then place the nanofiller in 200g of ethanol for ultrasonic dispersion to obtain a turbid liquid; 2) Mix the turbid liquid, 50g of 3-aminopropyltriethoxysilane and 10g of benzotriazole at 50℃ for 1h to obtain mixture 1; 3) Dissolve 100g of isocyanate (hexamethylene diisocyanate) and 80g of organosilicon diol (organosilicon polyether diol) in 50g of ethanol to obtain mixture 2; 4) Mixture 1 and mixture 2 are stirred and reacted at 60°C for 1 hour, filtered, and the filter residue is collected to obtain the modified nanofiller.

[0033] The organosilicon polyether diol is a hydroxyl-terminated organosilicon diol with a molecular weight of 1500.

[0034] The difference between Examples 5-6 and Example 4 lies in the types and amounts of some raw materials used in the preparation of the modified nanofillers, as well as the experimental parameters. Specific differences are shown in Table 2. Table 2. Types, amounts, and experimental parameters of raw materials used in the preparation of modified nanofillers in Examples 4-6.

[0035] Example 7 A waterproof bio-based polyurethane coating, the difference between this embodiment and Example 1 is that the chain extender is obtained by mixing diethyltoluenediamine and ethanolamine in a weight ratio of 3:1.

[0036] Example 8 A waterproof bio-based polyurethane coating, the difference between this embodiment and Example 4 is that the chain extender is obtained by mixing diethyltoluenediamine and ethanolamine in a weight ratio of 4:1.

[0037] Example 9 A waterproof bio-based polyurethane coating, the difference between this embodiment and Example 1 is that the wetting agent is composed of nonylphenol polyoxyethylene ether and polyoxyethylene fatty alcohol ether in a weight ratio of 5:3.

[0038] Example 10 A waterproof bio-based polyurethane coating, the difference between this embodiment and Example 4 is that the wetting agent is composed of nonylphenol polyoxyethylene ether and polyoxyethylene fatty alcohol ether in a weight ratio of 6:3.

[0039] Example 11 A waterproof bio-based polyurethane coating, the difference between this embodiment and Example 1 is that the diluent is obtained by mixing ethanol and an ester solvent (ethyl acetate) in a weight ratio of 7:10.

[0040] Example 12 A waterproof bio-based polyurethane coating, the difference between this embodiment and Example 4 is that the diluent is obtained by mixing ethanol and an ester solvent (ethyl acetate) in a weight ratio of 8:10. Comparative Example

[0041] Comparative Example 1 A waterproof bio-based polyurethane coating, the difference between this embodiment and Example 1 is that tung oil polyol is used instead of an equal mass of castor oil polyester polyol.

[0042] Comparative Example 2 A waterproof bio-based polyurethane coating, the difference between this embodiment and Example 1 is that a solvent is used instead of an equal mass of bio-based polyacid.

[0043] Comparative Example 3 A waterproof bio-based polyurethane coating, the difference between this embodiment and Example 1 is that the amount of castor oil polyester polyol used is 500g and the amount of solvent used is 34g.

[0044] Comparative Example 4 A waterproof bio-based polyurethane coating, the difference between this embodiment and Example 1 is that the amount of castor oil polyester polyol used is 200g and the amount of solvent used is 253g.

[0045] Comparative Example 5 A waterproof bio-based polyurethane coating, the difference between this embodiment and Example 1 is that the amount of modified nanofiller is 250g and the amount of solvent is 153g.

[0046] Detection methods / test methods

[0047] Tensile strength: Tested in accordance with GB / T19250-2003 "Polyurethane Waterproof Coatings".

[0048] High and low temperature resistance: Tested according to the test standard GB / T1735-2009. The low temperature is -40℃ for 24 hours and the high temperature is 250℃ for 24 hours. The cycle is 20 times. Observe the coating for phenomena such as bubbles, peeling, cracking and discoloration. If there are no phenomena, the tensile strength is measured and the tensile strength retention rate is calculated.

[0049] UV aging resistance test: The coatings prepared in Examples 1-12 and Comparative Examples 1-5 were applied to the substrate and dried. They were then irradiated with ultraviolet light under the conditions of a xenon arc lamp aging test chamber with a cumulative irradiation of 2000 MJ / ㎡ for 1000h. The coatings were observed for phenomena such as bubbles, peeling, cracking and discoloration. If no such phenomena were observed, the tensile strength was measured and the retention rate of tensile strength was calculated.

[0050] Wear resistance: Tested according to GB / T 1768 test standard.

[0051] Flowability: Tested according to GB / T 9264 standard. Test data are shown in Table 3. Table 3 Experimental data of Examples 1-12 and Comparative Examples 1-5

[0052] As can be seen from Examples 1-12 and Comparative Examples 1-5 and in conjunction with Table 3, the waterproof bio-based polyurethane coatings prepared by the formulation in this application have good strength, high and low temperature resistance, weather resistance, abrasion resistance and flowability, and can adapt to complex environmental changes.

[0053] Compared with Comparative Examples 1-2, the tensile strength of Comparative Example 1 was lower than that of Example 1. In the high and low temperature resistance and UV resistance tests, Comparative Examples 1-2 showed cracking, bubbling and discoloration. In the abrasion resistance test, Comparative Example 1 had more losses and poor flowability. This indicates that the use of castor oil polyol, bio-based polyacid and other raw materials together can improve the strength, high and low temperature resistance, weather resistance, abrasion resistance and flowability of waterproof bio-based polyurethane coatings.

[0054] Compared with Comparative Examples 3-5, the tensile strength of Comparative Examples 3-5 decreased; in the high and low temperature resistance test and the UV resistance test, Comparative Example 4 showed cracking and bubbling, and the retention rate of Comparative Example 5 decreased; in the abrasion resistance test, Comparative Examples 3-5 had more losses and poor flowability, indicating that optimizing the amount of castor oil polyether polyol and modified nanofiller is beneficial to improving the strength, high and low temperature resistance, weather resistance, abrasion resistance and flowability of waterproof bio-based polyurethane coatings.

[0055] Compared with Examples 1 and Examples 4-6, Examples 4-6 show improved tensile strength, improved retention of high and low temperature resistance and UV resistance, reduced loss after abrasion test, and improved fluidity. This indicates that the modified nanofiller prepared in this application can improve the strength, high and low temperature resistance, weather resistance, abrasion resistance and fluidity of waterproof bio-based polyurethane coatings.

[0056] The experimental results from Examples 1 and 7, and Examples 4 and 8 show that optimizing the type and amount of chain extender can improve the strength, high and low temperature resistance, weather resistance and wear resistance of waterproof bio-based polyurethane coatings.

[0057] The experimental results from Examples 1 and 9, and Examples 4 and 10 show that optimizing the type and amount of wetting agent can improve the strength, weather resistance, abrasion resistance and flowability of waterproof bio-based polyurethane coatings.

[0058] Examples 1 and 11, and Examples 4 and 12 show that optimizing the type and amount of diluent can improve the abrasion resistance and flowability of waterproof bio-based polyurethane coatings.

[0059] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A waterproof bio-based polyurethane coating, characterized in that, It is prepared from the following raw materials by weight percentage: Castor oil polyester polyols 25-40% Isocyanates 15-25% Bio-based polyacids 5-10% Catalyst 0.2-0.6% Chain extender 0.5-1% Modified nanofillers 15-20% wetting agent 3-5% 1-2% of curing agent The remainder is diluent.

2. The waterproof bio-based polyurethane coating according to claim 1, characterized in that, The modified nanofiller was prepared by the following method: 1) Dry the nanofiller, then place it in ethanol and ultrasonically disperse it to obtain a turbid liquid; 2) Stir the turbid liquid, 3-aminopropyltriethoxysilane and benzotriazole at 50-70℃ for 1-2 hours to obtain mixture 1; 3) Dissolve isocyanate and organosilicon diol in ethanol to obtain mixture 2; 4) Mixture 1 and mixture 2 are stirred and reacted at 60-70℃ for 1-2 hours, filtered, and the filter residue is collected to obtain the modified nanofiller.

3. A waterproof bio-based polyurethane coating according to claim 2, characterized in that, The raw materials used to prepare the modified nanofiller are as follows by weight: 30-40 parts of nanofiller 5-8 parts of aminopropyltriethoxysilane 1-3 parts of benzotriazole 10-13 parts isocyanate 8-10 parts of organosilicon diol 25-35 parts ethanol.

4. The waterproof bio-based polyurethane coating according to claim 2, characterized in that: The average particle size of the nanofiller is 20-300 nm.

5. The waterproof bio-based polyurethane coating according to claim 1, characterized in that: The diluent is obtained by mixing ethanol and an ester solvent in a weight ratio of (7-8):10, wherein the ester solvent is one of ethyl acetate, butyl acetate, and dimethyl carbonate.

6. The waterproof bio-based polyurethane coating according to claim 4, characterized in that: The castor oil polyester polyol has a hydroxyl value of 85-150 mgKOH / g and a functionality of 1-3.

7. The waterproof bio-based polyurethane coating according to claim 1, characterized in that: The bio-based polyacid is one of furanyl dicarboxylic acid, palmitic acid, oleic acid, malic acid, and citric acid.

8. The waterproof bio-based polyurethane coating according to claim 1, characterized in that: The chain extender is obtained by mixing diethyltoluenediamine and ethanolamine in a weight ratio of (3-4):

1.

9. The waterproof bio-based polyurethane coating according to claim 1, characterized in that: The wetting agent is obtained by mixing nonylphenol polyoxyethylene ether and polyoxyethylene fatty alcohol ether in a weight ratio of (5-6):

3.

10. A preparation process for a waterproof bio-based polyurethane coating as described in any one of claims 1-9, characterized in that, The preparation steps include the following: S1. Under dry nitrogen protection, castor oil polyester polyol is added to the reaction vessel, heated to 110-120℃ and dehydrated under reduced pressure, and then the system temperature is reduced to 60-80℃. S2. Add bio-based polyacid, isocyanate and catalyst to the reaction vessel, mix well, adjust the viscosity of the mixture with solvent, and maintain the reaction at 60-80℃ for 7-9 hours. After the reaction in step S2 is completed, a chain extender is added to carry out a crosslinking reaction. The mixture is stirred, and then modified nanofillers, wetting agents, curing agents and diluents are added and stirred to obtain a bio-based polyurethane coating.

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