Tung oil-epoxy soybean oil based aqueous polyurethane dispersions and methods of making the same
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SOUTH CHINA AGRICULTURAL UNIVERSITY
- Filing Date
- 2023-11-17
- Publication Date
- 2026-06-05
Smart Images
Figure CN117487111B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of waterborne polyurethane materials technology, specifically to tung oil-epoxy soybean oil-based waterborne polyurethane dispersions and their preparation methods. Background Technology
[0002] Waterborne polyurethane is a polyurethane system that uses water as a diluent and dispersant. Its synthesis generally employs an internal emulsification method, where hydrophilic chain extenders are grafted onto hydrophobic polyurethane chains, followed by the addition of a neutralizing agent to form a salt, and finally, high-speed stirring to emulsify and disperse it in water. Compared to solvent-based polyurethane, waterborne polyurethane also possesses properties such as weather resistance, abrasion resistance, high flexibility, high tensile strength, and high adhesion, but it has lower viscosity, produces less pollution, and is not only easier to apply but also safer and more reliable. Furthermore, it contains virtually no volatile organic compounds, making it considered a green and environmentally friendly chemical product. However, waterborne polyurethane also has some drawbacks, such as slow drying speed, poor substrate wettability, and poor water resistance. Currently, the soft segments used in the synthesis of waterborne polyurethane are mostly petroleum-based polyether diols or polyester diols, which are not only non-renewable but also difficult to degrade, causing pollution to the environment. Summary of the Invention
[0003] The purpose of this invention is to provide a tung oil-epoxidized soybean oil-based waterborne polyurethane dispersion and its preparation method, so as to solve at least one of the above-mentioned technical problems.
[0004] According to one aspect of the present invention, a tung oil-epoxidized soybean oil-based aqueous polyurethane dispersion is provided, the preparation method of which includes the following steps:
[0005] Take epoxidized soybean oil-tung oil ester, hydrophilic chain extender, internal emulsifier, crosslinking agent diisocyanate, catalyst A and organic solvent, mix them, and react them at a temperature of 60-80℃ for 3-5 hours to obtain the first reaction mixture;
[0006] The first mixture was cooled to room temperature, and an aminosilane coupling agent was added to continue the reaction for 0.5 to 2 hours. Then, a neutralizing agent was added to neutralize the mixture, and the prepolymer was obtained.
[0007] Water is added to the prepolymer, and after emulsification, the organic solvent in the emulsion is removed to obtain the final product.
[0008] This invention synthesizes a plant oil-based waterborne polyurethane dispersion with high bio-based content using epoxidized soybean oil-tetrafluoroethylene ester (TESO) as the main component. On the one hand, it can reduce the use of petrochemical resources and increase the bio-based content in waterborne polyurethane coatings. On the other hand, the long-chain fatty acid structure of epoxidized soybean oil can endow the cured film with flexibility, increasing the crosslinking density of the cured film while ensuring its flexibility, thus giving the cured film excellent comprehensive performance. The conjugated double bonds on the tetrafluoroethylene ester also help improve the hardness, adhesion, crosslinking density, corrosion resistance and other properties of the cured film after curing. At the same time, the plant oil-based waterborne polyurethane dispersion of this application can be cured into a film without the need for additional modification with petroleum-based raw materials containing terminal double bonds and UV curing.
[0009] The tung oil-epoxy soybean oil-based waterborne polyurethane dispersion provided by this invention is cured into a film mainly by room temperature drying, supplemented by subsequent curing with oxygen in the air. The resulting cured film has excellent tensile properties and maintains a high elongation at break while having strong tensile strength.
[0010] In some embodiments, the hydrophilic chain extender may be selected from at least one of butanediol, ethylene glycol, propylene glycol, and hexanediol.
[0011] In some embodiments, the internal emulsifier may be selected from at least one of N-methyldiethanolamine, N,N-dimethylethanolamine, N,N-bis(hydroxymethyl)tert-butylamine, and 3-dimethylamino-1,2-propanediol.
[0012] In some embodiments, the molar ratio of hydroxyl groups in epoxidized soybean oil-tung oil ester, hydrophilic chain extender, and internal emulsifier can be (4-5):(1-3):(5-7).
[0013] In some embodiments, the diisocyanate may be selected from at least one of isophorone diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, and lysine diisocyanate.
[0014] In some embodiments, the molar ratio of the isocyanate groups in the diisocyanate to the total amount of hydroxyl groups in the epoxidized soybean oil-tung oil ester, hydrophilic chain extender, and internal emulsifier can be 1:(0.9 to 0.95).
[0015] In some embodiments, the aminosilane coupling agent is selected from at least one of aminopropyltriethoxysilane, aminopropyltrimethoxysilane, aminopropylmethyldiethoxysilane, and N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane.
[0016] In some embodiments, the amount of aminosilane coupling agent used is 1% to 4% of the total mass of epoxidized soybean oil-tung oil ester, hydrophilic chain extender, internal emulsifier and diisocyanate.
[0017] In some embodiments, catalyst A may be selected from at least one of dibutyltin dilaurate, dibutyltin diacetate, stannous octoate, dialkyltin dimaleate, dithioalkyltin, and zinc naphthenate.
[0018] In some embodiments, the amount of catalyst A may be 0.05% to 1% of the total mass of epoxidized soybean oil-ketoester, hydrophilic chain extender, internal emulsifier, and diisocyanate.
[0019] In some embodiments, the organic solvent may be selected from at least one of acetone and butanone.
[0020] In some embodiments, the amount of organic solvent used can be 30% to 50% of the total mass of epoxidized soybean oil-ketoester, hydrophilic chain extender, internal emulsifier, and diisocyanate.
[0021] In some embodiments, the neutralizing agent may be selected from at least one of phosphoric acid, hydrochloric acid, and acetic acid.
[0022] In some embodiments, the amount of neutralizing agent can be 90% to 100% of the molar amount of the internal emulsifier.
[0023] In some embodiments, the mass ratio of water to prepolymer can be (3-8):(2-3).
[0024] In some embodiments, the preparation method of epoxidized soybean oil-tung oil ester may include the following steps:
[0025] Epoxidized soybean oil, tung oil acid, catalyst B and polymerization inhibitor are mixed and reacted at a temperature of 110-130℃ under a protective gas until the acid value of the reaction system is lower than 10 mg KOH / g, thus obtaining epoxidized soybean oil-tung oil acid ester.
[0026] In some embodiments, the molar ratio of epoxidized soybean oil to tung oil acid is (1-1.2):(3-3.5).
[0027] In some embodiments, catalyst B may be selected from at least one of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), triphenylphosphine, N,N-dimethylbenzylamine, and tetrabutylammonium bromide; the amount of catalyst B may be 0.5% to 1% of the total mass of epoxidized soybean oil and tung oil acid.
[0028] In some embodiments, the polymerization inhibitor may be selected from at least one of hydroquinone, p-methoxyphenol, 2-tert-butylhydroquinone, and methylhydroquinone; and its amount may be 0.5% to 1.5% of the mass of tung oil acid.
[0029] In some embodiments, the protective gas may be selected from at least one of nitrogen and inert gases. Attached Figure Description
[0030] Figure 1 A schematic diagram of the synthetic route for epoxidized soybean oil-tetramethyl ester (TESO);
[0031] Figure 2 Infrared spectra of tung oil (TO), tung oil acid (TOA), and TESO;
[0032] Figure 3 For TOA and TESO 1 H NMR spectrum;
[0033] Figure 4 A schematic diagram of the synthesis route for tung oil-epoxidized soybean oil-based waterborne polyurethane dispersion (WPU);
[0034] Figure 5 ATR-FTIR spectra of TESO, WPU, and cured films;
[0035] Figure 6 The particle size distribution curve of WPU;
[0036] Figure 7 A digital photograph of the WPU's appearance;
[0037] Figure 8 The graph shows the relationship between the storage modulus (E'), loss factor (Tanδ), and temperature of the WPU cured film.
[0038] Figure 9 The stress-strain curve of the WPU cured film;
[0039] Figure 10 TGA(a) and DTG(b) curves of the WPU cured film;
[0040] Figure 11 The gelation rate of the WPU cured film;
[0041] Figure 12 The water absorption rate and water contact angle of the WPU cured film. Detailed Implementation
[0042] The present invention will be further described in detail below with reference to the embodiments. The embodiments are for illustrative purposes only and do not limit the invention in any way. Unless otherwise specified, the raw materials and reagents used in the embodiments are conventional products that can be obtained commercially; experimental methods that do not specify specific conditions in the embodiments are generally performed under conventional conditions in the art or according to the conditions recommended by the manufacturer.
[0043] In this invention, tung oil acid (TOA) can be synthesized with reference to methods disclosed in the prior art, such as: Liang B, Kuang S, Huang J, et al. Synthesis and characterization of novel renewable tung oil-based UV-curable active monomers and bio-based copolymers[J]. Progress in Organic Coatings, 2019, 129: 116-124.
[0044] For example, a specific method for synthesizing a TOA may include the following steps:
[0045] 20.00 g of tung oil (TO, industrial grade, manufactured by Shandong Lvcheng Chemical Co., Ltd.), 6.00 g of KOH, 5 g of deionized water, and 50.00 mL of ethanol were added separately to a 250 mL three-necked flask equipped with a thermometer, reflux condenser, and mechanical stirrer. After stirring until homogeneous, the temperature was raised to 95 °C and the reaction mixture was stirred continuously at this temperature for 1 h. Subsequently, 5 mol / L hydrochloric acid solution was added dropwise to the reaction mixture to neutralize it until the pH dropped to 2–3. The mixture was then cooled to room temperature and filtered to obtain the filtrate. The filtrate was then separated and the crude organic product was collected using a separatory funnel. The crude product was dissolved in a large amount of anhydrous ethanol and refrigerated overnight. Finally, slightly orange-yellow crystalline tung oil acid (TOA) was obtained by rotary evaporation.
[0046] Preparation of Tung Oil-Epoxy Soybean Oil-Based Waterborne Polyurethane Dispersions (WPU) in Examples 1-5
[0047] In Examples 1-5, the molar ratios of isocyanate groups (NCO) in diisocyanate (isophorone diisocyanate IPDI), hydroxyl groups in epoxidized soybean oil-tung oil ester (TESO), hydroxyl groups in hydrophilic chain extender (1,4-butanediol BOD), and hydroxyl groups in internal emulsifier (N-methyldiethanolamine MDEA), as well as the amount of aminosilane coupling agent (KH550), are shown in Table 1.
[0048] Table 1. Composition of Tung Oil-Epoxy Soybean Oil-Based Waterborne Polyurethane Dispersion
[0049]
[0050] The preparation method includes the following steps:
[0051] (1) Synthesis of epoxidized soybean oil-tetramethyl ester (TESO)
[0052] Take 9.75 g (0.01 mol) of epoxidized soybean oil (ESO, analytical grade, manufactured by Shanghai Maclean Biochemical Co., Ltd.), 8.34 g (0.03 mol) of TOA, 0.18 g of catalyst DBU and 0.09 g of hydroquinone and put them into a 250 ml three-necked round-bottom flask equipped with a mechanical stirrer and a vent. Under nitrogen purging, heat to 120 °C and stir until the acid value of the reaction system is lower than 10 mg KOH / g and then stop the reaction to finally obtain a brown viscous liquid product (TESO).
[0053] The synthetic route for epoxidized soybean oil-tetramethyl ester (TESO) is as follows: Figure 1 As shown.
[0054] The images were recorded at 4000-500 cm⁻¹ using a VERTEX 80 FT-IR spectrometer from Bruker, Germany. -1 Fourier transform infrared (FT-IR) spectra of TO, TOA, and TESO within the range, with a resolution of 2 cm⁻¹. -1 The number of scans was 32. The results are as follows: Figure 2 As shown.
[0055] like Figure 2 As shown, in the infrared spectrum of TO, 1744 cm⁻¹ -1 The absorption peak at 3014 cm⁻¹ is due to the -C=O- vibration of the ester group. -1 and 991cm -1 The peak at 1744 cm⁻¹ corresponds to the =CH deformation vibration absorption peak of the unsaturated conjugated carbon-carbon double bond in the aliphatic chain. By comparing the infrared spectra of TO and TOA, it can be found that the peak at 1744 cm⁻¹ in TOA is... -1 The characteristic absorption peak at 1709 cm⁻¹ disappears, replaced by a peak at 1709 cm⁻¹. -1 An absorption peak belonging to the -C=O- vibration of the carboxyl group structure appeared at [location missing]; in addition, an absorption peak appeared in the range of 3500–2500 cm⁻¹. -1 A broad and strong infrared absorption band appeared at [value missing], which is a characteristic absorption peak of the carboxyl group, indicating the successful synthesis of the intermediate product tung oil acid (TOA). In the TESO infrared spectrum, it is located at 3500–2500 cm⁻¹. -1 The characteristic absorption band at 3467 cm⁻¹ basically disappears, and at 3467 cm⁻¹... -1 A new infrared characteristic absorption peak belonging to the hydroxyl group on TESO appeared, indicating that a ring-opening esterification reaction successfully occurred between the carboxylic acid group of TOA and the epoxy group of ESO, and TESO polyol was synthesized.
[0056] The proton NMR spectra of TOA and TESO were recorded using a Bruker AV600 NMR spectrometer. 11H NMR was performed using CDCl3 as the solvent. The 1H NMR spectra of TOA and TESO are shown below. Figure 3 As shown.
[0057] like Figure 3 As shown, in TOA, the chemical shift peak at 5.35–6.50 ppm represents the proton peak of the unsaturated conjugated double bond on the fatty acid chain, and no methylene or methine proton peaks from the triglyceride structure of tung oil were observed in the 4.80–5.20 ppm range. This indicates that the tung oil was reacted almost completely, and the intermediate tung oil acid (TOA) was successfully synthesized. For TESO, a new proton peak appeared in the 4.80–5.20 ppm range, which is attributed to the H proton peak of the methine group attached to the ester group. Simultaneously, a new chemical shift peak appeared in the 3.88–3.97 ppm range, representing the H proton peak on the carbon atom attached to the hydroxyl group, which is produced by the ring-opening esterification of the carboxyl group and the epoxy group. Furthermore, no hydrogen proton peak of the epoxy group in the epoxidized soybean oil structure was found in the 2.86–3.20 ppm range. These results indicate that the epoxy group in the epoxidized soybean oil underwent a ring-opening esterification reaction with the carboxyl group in TOA, and the reaction was relatively complete, further confirming the successful synthesis of TESO.
[0058] (2) Synthesis of epoxidized soybean oil-tung oil ester-based waterborne polyurethane dispersion (WPU)
[0059] S1: TESO, N-methyldiethanolamine, 1,4-butanediol, and isophorone diisocyanate were added to a three-necked round-bottom flask equipped with a mechanical stirrer and a reflux condenser. 0.5 wt% (based on the total mass of epoxidized soybean oil-ketoester, N-methyldiethanolamine, 1,4-butanediol, and isophorone diisocyanate) of dibutyltin dilaurate was added as a reaction catalyst. During the reaction, 50 wt% (based on the total mass of epoxidized soybean oil-ketoester, N-methyldiethanolamine, 1,4-butanediol, and isophorone diisocyanate) of acetone solvent could be added to reduce the viscosity of the system. The reaction temperature was raised to 70°C and stirred continuously for 4 hours to obtain the first reaction mixture.
[0060] S2: Then, the first reaction mixture was cooled to room temperature and aminopropyltriethoxysilane (KH550) was added to continue the reaction for 1 hour; subsequently, an equimolar amount of N-methyldiethanolamine neutralizing agent phosphoric acid was added to neutralize the reaction product and the mixture was stirred for 0.5 hours to obtain the prepolymer;
[0061] S3: Finally, add 7 / 3 times the mass of deionized water to the prepolymer and emulsify by high-speed stirring for 2 hours; remove acetone from the emulsion by rotary evaporator to obtain an epoxy soybean oil-tung oil ester-based waterborne polyurethane dispersion (WPU) with a solid content of about 30%.
[0062] The synthesis route of WPU is as follows Figure 4As shown.
[0063] The epoxy soybean oil-tung oil ester-based aqueous polyurethane dispersions prepared in Examples 1 to 5 are named F1 to F5 respectively.
[0064] The epoxy soybean oil-tung oil ester-based aqueous polyurethane dispersions prepared in Examples 1-5 were poured into plastic petri dishes and cured at room temperature to obtain cured films. To ensure complete curing, the cured films needed to be dried at room temperature for at least one month before testing.
[0065] The curing behavior of the cured film before and after curing was studied using AFT-IR total reflectance infrared spectroscopy. A Bruker Vertex 70 AFT-IR spectrometer was used in the range of 4000–500 cm⁻¹. -1 The structure of the cured coating was characterized within the wavenumber range.
[0066] Infrared spectra of TESO, the dispersion before and after curing, and the cured film (KH550 content 3wt%) are as follows: Figure 5 As shown.
[0067] like Figure 5 As shown, the hydroxyl absorption peak of TESO polyol is at 3466 cm⁻¹. -1 The [polymer] disappeared at [location], while a new [polymer] appeared in the prepolymer at 3334 cm⁻¹. -1 The strong absorption peak corresponds to the NH stretching vibration of the urethane bond, indicating that the hydroxyl group of TESO reacts almost completely with the isocyanate group of isophorone diisocyanate, successfully introducing it into the long polyurethane chain. Simultaneously, a peak at 2268 cm⁻¹ was observed in the spectrum of the prepolymer. -1 A relatively small absorption peak appeared at 991 cm⁻¹, corresponding to the characteristic absorption peak of -NCO, indicating that an NCO-terminated polyurethane prepolymer was synthesized. In the spectrum of the cured coating, the peak originally at 991 cm⁻¹ can be seen... -1 The disappearance of the absorption peak attributed to the carbon-carbon conjugated double bond indicates that oxidative polymerization crosslinking has been successfully performed. Furthermore, at 1046 cm⁻¹... -1 The peaks appearing at this point are attributed to the Si-O-Si bonds generated after the hydrolysis and condensation of KH550, forming an interpenetrating polymer network structure.
[0068] Experimental Example 1: Stability Analysis of WPU Emulsion
[0069] The particle size distribution and zeta potential of the WPU emulsion were studied and tested using a Malvern Zeta-sizer Nano ZSE (Malvern Instruments). Before testing, all dispersions were diluted with distilled water to prepare test samples, with a dilution factor of 100-fold. The particle size distribution curve and appearance photographs of the WPU emulsion are shown below. Figure 6 and Figure 7 As shown in Table 2, the specific values of its average particle size, dispersion index (PDI), zeta potential, etc.
[0070] As shown in Table 2, the WPU without KH550 had the smallest particle size at 43.39 nm. The particle size of the WPU increased with increasing KH550 content. All WPU emulsions had a PDI less than 0.3 and an absolute value of zeta potential greater than 40 mV, indicating that the epoxy soybean oil-tung oil ester-based aqueous polyurethane dispersion provided by this invention has good emulsion storage stability.
[0071] A certain amount of the emulsion was centrifuged at 3000 r·min⁻¹ for 15 minutes at room temperature. No precipitation was observed. Therefore, it can be considered that the storage stability of all emulsions exceeds 6 months.
[0072] Table 2 Physical parameters of different WPU emulsions
[0073] sample Average particle size (nm) Dispersion Index (PDI) Zeta potential (mV) Emulsion Appearance F1 43.39±0.29 0.138±0.004 41.73±1.92 Orange Transparent F2 45.17±0.23 0.138±0.006 47.67±2.15 Orange Transparent F3 57.95±0.33 0.228±0.005 42.97±0.33 Orange Transparent F4 151.47±0.94 0.186±0.002 60.10±1.43 Orange-white opaque F5 168.87±1.58 0.197±0.016 56.90±0.36 Milky white and opaque
[0074] Experimental Example 2: Dynamic Mechanical Analysis of Cured Film
[0075] Dynamic mechanical analysis of the specimens was performed using a Netzsch DMA 242C dynamic thermomechanical analyzer. The specimen dimensions were 20.0 mm × 6.0 mm × 0.5 mm (length × width × thickness). The tensile mode frequency used was 1 Hz, the test temperature range was -80 to 170 °C, and the heating rate was 3 °C / min. The temperature corresponding to the peak value of the Tanδ curve is the glass transition temperature of the specimen.
[0076] The glass transition temperature (Tg) of the cured film was obtained through dynamic mechanical analysis. g The relationship between energy storage modulus (E') and loss factor (Tanδ) is shown in the following results. Figure 8 As shown in the figure, the peak value in the Tanδ curve corresponds to the glass transition temperature of the cured film, and each Tanδ curve shows only one peak, indicating that the soft and hard segments in the cured film have good compatibility. Figure 8 It can be seen that the high storage modulus of the cured film is mainly observed in the low temperature region, and the storage modulus of the cured film decreases rapidly as the temperature increases. This is because the cured film changes from its original glassy state to a highly elastic state.
[0077] Thermomechanical properties of cured films and crosslinking density (ν) e Closely related to the crosslinking density of the cured film, the crosslinking density can be calculated using the following formula (eq 1.1):
[0078] E'=3RT'×ν e (eq 1.1)
[0079] Where T' is the cured film in the rubber state (T g The absolute temperature at +30℃, E' is the storage modulus of the cured film at T', and R is the gas constant.
[0080] E' was derived and calculated through DMA analysis. 25 T g , E' and ν e The values are listed in Table 3.
[0081] Table 3 Dynamic mechanical properties and crosslinking density of WPU cured film
[0082]
[0083]
[0084] Mechanical property analysis of the cured film in Experiment Example 3
[0085] The tensile properties of the cured film were tested using a UTM 4204 universal testing machine manufactured by Shenzhen Sansi. The crosshead speed was set to 20 mm / min, and the sample size was 40.0 mm × 10.0 mm × 0.5 mm (length × width × thickness). To ensure the accuracy of the experimental results, all samples were tested at least 5 times, and the average value was taken.
[0086] The tensile properties test results of the cured film are as follows: Figure 9 As shown in Table 4, the results indicate that the cured film exhibits good tensile properties, with tensile strength generally exceeding 20 MPa and elongation at break exceeding 80%. This demonstrates the excellent flexibility of the cured film. This is because the system not only contains the soft-segment long-chain structure of epoxidized soybean oil, but also that the unsaturated conjugated double bonds on TESO form a tight cross-linked network after undergoing oxidative polymerization. The combined effect of these two factors endows the cured film with excellent tensile properties. With the increase of KH550 addition, the tensile strength of the cured film slightly increases, while the elongation at break gradually decreases. This is mainly because the -Si-O-C2H5 groups in KH550 form a Si-O-Si structure after hydrolysis and condensation, making the cross-linked network of the system tighter and making the migration of free segments more difficult. In addition, the increase of KH550 dosage will form more hydrogen bonds, enhancing the hydrogen bond forces in the system and thus improving the tensile strength of the cured film. However, due to the low amount of KH550 added, the crosslinking density of the cured film was not significantly different, so the tensile strength and elongation at break of the cured film did not change significantly overall.
[0087] Table 4 Mechanical properties of WPU cured film
[0088] sample Tensile strength (MPa) Elongation at break (%) Young's modulus (MPa) F1 19.35±0.14 122.82±0.40 15.84±0.08 F2 20.21±0.83 113.36±5.48 17.84±0.13 F3 18.91±0.43 83.52±0.84 22.65±0.40 F4 22.04±0.72 110.13±3.46 20.01±0.65 F5 23.40±1.43 108.77±2.37 21.49±1.32
[0089] Thermogravimetric Analysis of Cured Film in Experiment Example 4
[0090] Thermogravimetric analysis (TGA) of the experimental samples was performed using a Netzsch STA 449C thermal analyzer under a nitrogen atmosphere. The nitrogen flow rate was set to 20 ml / min, the test temperature range was 30-900℃, and the heating rate was 10℃ / min.
[0091] Figure 10 These are the TGA and DTG curves of the cured film, and the temperature at which the cured film degrades to 5% (T). 5％ ), the temperature at which 50% degradation occurs (T) 50％ ), temperature of maximum thermal degradation rate (T) max ) and residual carbon rate (W) char The results are listed in Table 5, where the carbon residue was measured at 800℃.
[0092] The results show that with the continuous increase of KH550 content, the thermal degradation temperature of the cured film at each stage generally increases. This is because the modified molecular chain has an ethoxy structure, which forms a Si-O-Si structure after hydrolysis and condensation reactions. This structure increases the crosslinking density of the system, restricts the relative migration of molecular chains, and thus improves the thermal stability of the cured film. Simultaneously, the bond energy of the Si-O bond is higher than that of the CO bond, requiring more heat to break it under the same conditions, thus increasing the thermal decomposition temperature of the system to a certain extent. Furthermore, the char residue of the film also increases from 8.27% to 9.04%. This is because Si elements form high-temperature resistant silicon dioxide at high temperatures and also promote the formation of more char layers, thereby mitigating mass loss and improving the high-temperature resistance of the material.
[0093] Table 5 Thermal decomposition data of WPU cured film
[0094] sample <![CDATA[T 5％ (℃)]]> <![CDATA[T 50％ (℃)]]> <![CDATA[T max (1 st / 2 nd )(℃)]]> Carbon residue rate (%) F1 203.5 361.4 286.5 / 365.5 8.27 F2 204.0 362.8 285.7 / 366.5 8.75 F3 200.4 364.0 287.7 / 370.0 8.83 F4 205.5 366.4 285.7 / 371.9 8.81 F5 210.9 364.1 294.1 / 370.2 9.04
[0095] Analysis of gelation rate of cured film in Experiment 5
[0096] The gel content in the cured film was determined using the acetone extraction method. First, a cured film of mass w0 was accurately weighed and immersed in a 20ml sealed glass bottle containing acetone at room temperature for 48 hours. Then, the cured film was removed and dried in a vacuum oven at 60℃ until constant weight, and its weight w1 was recorded. Finally, the gel rate of each cured film was calculated using formula (eq 1.2).
[0097] Gelation rate = (w1 / w0) × 100% (eq 1.2)
[0098] The results are as follows Figure 11As shown, with the continuous increase of KH550 content, the gelation rate of the cured film also gradually increased from 88.57% to 94.78%. This is because the addition of KH550 forms a Si-O-Si unit structure on the polymer, which acts as a physical crosslinking agent, thereby improving the density of the polymer network, hindering solvent penetration, and improving its solvent resistance. The gelation rates of the cured films were all higher than 88%, which demonstrates that all cured films have good curing ability. This is mainly attributed to the post-oxidative curing crosslinking behavior of the conjugated double bonds on the TESO structure.
[0099] Analysis of contact angle and water absorption rate of cured film in Experiment Example 6
[0100] The water contact angle of the cured film was determined using the water droplet method. A Powereach JC2000C1 goniometer was used to measure the water contact angle of the cured film. A portion of the cured film, weighed as m0, was immersed in water for 48 hours. The insoluble portion was removed, blotted dry with filter paper, and weighed as m1. This process was repeated three times, and the average value was taken. The water absorption rate of the cured film was calculated using the following formula.
[0101] Water absorption rate = (m1 - m0 / m0) × 100% (eq 1.3)
[0102] The results are as follows Figure 12 As shown in Table 6, the results indicate that the water contact angle and water absorption rate of the TESO cured film modified with KH550 are improved to some extent, and the water resistance of the cured film continuously increases with the increase of KH550 content. This is because the Si element in KH550 has low surface energy, and during the film formation process, the hydrophobic segments containing Si migrate to the surface, thereby reducing the surface tension of the cured film and increasing its water contact angle. In addition, the Si-containing segments form a Si-O-Si structure after hydrolysis and condensation reaction. This structure increases the crosslinking density of the cured film, enhances the compactness of the cured film surface, hinders water penetration, and reduces its water absorption rate; at the same time, the crosslinking structure of siloxane also leads to an increase in surface roughness, thus increasing the water contact angle of the cured film. As shown in Table 6, the water contact angle of the cured film increased from 72.06° to 93.85°, and the water absorption rate decreased from 11.52% to 5.82%.
[0103] Table 6. Water absorption rate and water contact angle of WPU cured film
[0104] sample Contact angle (°) Water absorption rate (%) gelation rate (%) F1 80.63±0.26 11.52±0.19 88.57±0.68 F2 82.28±0.18 10.04±0.16 89.48±0.73 F3 85.54±0.39 9.34±0.15 90.96±0.56 F4 88.20±0.44 8.04±0.12 92.52±0.64 F5 93.85±0.56 5.82±0.13 94.78±0.79
[0105] General performance analysis of the cured film in Experiment Example 7
[0106] Pencil Hardness Test: The pencil hardness of the cured coating is determined according to GB / T 6739-1996. The specific experimental method is as follows: The pencil hardness of the cured coating surface is measured using a hardness tester with a three-point contact method (two points are the rollers, and one point is the pencil lead). The angle between the pencil and the coating surface is adjusted to 45° with the hardness tester as the carrier. The hardness tester slides on the coating surface with a pressure of 1±0.05 kg and the damage condition of the coating surface after sliding is observed. Each sample is tested in parallel 5 times. When the coating breaks no more than 2 times, the pencil of the next higher hardness grade can be replaced for the next level of testing. When the coating breaks more than 2 times, the pencil grade can be read and the next grade can be recorded. The hardness grade range is divided into 6B~HB~6H from hardest to softest, with 6H being the hardest and 6B being the softest.
[0107] Flexibility Test: The flexibility of the cured coating is measured using the conical mandrel of a QTX-1731 coating elasticity testing machine, according to the test method of GB 1731-93. The minimum diameter of the conical mandrel that allows the cured film to be bent 180° around itself without cracking is the flexibility grade of the cured film. The conical mandrel models include... wait.
[0108] Adhesion test: The adhesion of the cured coating is tested according to the standard requirements of ASTM D3359, "Standard Test Method for Determining Adhesion Grades by Tape Test".
[0109] Chemical corrosion resistance test: At room temperature, weigh appropriate amounts of cured film samples and place them in sealed glass bottles containing tetrahydrofuran and chloroform, respectively. After soaking for 48 hours, remove the samples and observe the morphological changes of the cured films. Perform three parallel experiments on each group of samples to ensure the accuracy of the test.
[0110] The results are shown in Table 7.
[0111] The results showed that all TESO cured films had an adhesion rating of 0, indicating that the WPU cured films had good adhesion properties. This is mainly due to the hydrogen bonding between the urethane bonds unique to the polyurethane structure and the material surface. The pencil hardness of the WPU cured films all reached above 4H, primarily due to the oxidative polymerization of conjugated double bonds in TESO, resulting in more cross-linking bonds in the cured film and giving it good pencil hardness. Furthermore, with the increase of KH550, the pencil hardness of the cured film increased to 5H, because more Si-O-Si bonds were formed, increasing the cross-linking density of the system and thus improving the pencil hardness. The flexibility of all cured films reached above 2mm, which is attributed to the long, flexible fatty acid chains in the TESO structure, which is the soft segment of the system; therefore, these cured films exhibited good flexibility. Chemical resistance tests were conducted on the cured films using tetrahydrofuran or chloroform. After immersing the cured films for 48 hours, no significant changes were observed in any of the cured films, indicating that the cured films have a dense network structure, thereby preventing the penetration and dissolution of chemical reagents. This demonstrates their excellent chemical corrosion resistance.
[0112] Table 7 General Properties of WPU Cured Film
[0113]
[0114] The above descriptions are merely some embodiments of the present invention. Those skilled in the art can make various modifications and improvements without departing from the inventive concept of the present invention, and these all fall within the scope of protection of the present invention.
Claims
1. A method for preparing a tung oil-epoxidized soybean oil-based aqueous polyurethane dispersion, characterized in that, Includes the following steps: Take epoxidized soybean oil-tung oil ester, hydrophilic chain extender, internal emulsifier, diisocyanate, catalyst A and organic solvent, mix them, and react them at a temperature of 60~80℃ for 3~5 h to obtain the first reaction mixture; The first mixture was cooled to room temperature, and an aminosilane coupling agent was added to continue the reaction for 0.5 to 2 hours. Then, a neutralizing agent was added to neutralize the mixture, and the prepolymer was obtained. Water is added to the prepolymer, and after emulsification, the organic solvent in the emulsion is removed to obtain the final product; wherein, The hydrophilic chain extender is selected from at least one of butanediol, ethylene glycol, propylene glycol, and hexanediol; The internal emulsifier is selected from at least one of N-methyldiethanolamine, N,N-bis(hydroxymethyl)tert-butylamine, and 3-dimethylamino-1,2-propanediol. The preparation method of the epoxidized soybean oil-tung oil ester includes the following steps: Epoxidized soybean oil, tung oil acid, catalyst B and polymerization inhibitor are mixed and reacted at a temperature of 110~130℃ under a protective gas until the acid value of the reaction system is lower than 10 mg KOH / g, thus obtaining epoxidized soybean oil-tung oil ester.
2. The preparation method according to claim 1, characterized in that, The molar ratio of hydroxyl groups in the epoxidized soybean oil-tung oil ester, hydrophilic chain extender, and internal emulsifier is (4~5):(1~3):(5~7); the molar ratio of the isocyanate groups in the diisocyanate to the total amount of hydroxyl groups in the epoxidized soybean oil-tung oil ester, hydrophilic chain extender, and internal emulsifier is 1:(0.9~0.95).
3. The preparation method according to claim 1 or 2, characterized in that, The aminosilane coupling agent is selected from aminopropyltriethoxysilane, aminopropyltrimethoxysilane, and aminopropylmethyldiethoxysilane. N At least one of (2-aminoethyl)-3-aminopropylmethyldimethoxysilane; the amount of the aminosilane coupling agent is 1% to 4% of the total mass of epoxidized soybean oil-tung oil ester, hydrophilic chain extender, internal emulsifier and diisocyanate.
4. The preparation method according to claim 3, characterized in that, The diisocyanate is selected from at least one of isophorone diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, and lysine diisocyanate; the catalyst A is selected from at least one of dibutyltin dilaurate, dibutyltin diacetate, stannous octoate, dialkyltin dimaleate, dithioalkyltin disulfide, and zinc naphthenate.
5. The preparation method according to claim 4, characterized in that, The neutralizing agent is selected from at least one of phosphoric acid, hydrochloric acid, and acetic acid.
6. The preparation method according to claim 1, characterized in that, The molar ratio of epoxidized soybean oil to tung oil acid is (1~1.2):(3~3.5); the amount of catalyst B is 0.5%~1% of the total mass of epoxidized soybean oil and tung oil acid; the amount of polymerization inhibitor is 0.5%~1.5% of the mass of tung oil acid.
7. The preparation method according to claim 6, characterized in that, The catalyst B is selected from at least one of 1,8-diazabicyclo[5.4.0]undec-7-ene, triphenylphosphine, N,N-dimethylbenzylamine, and tetrabutylammonium bromide; the polymerization inhibitor is selected from at least one of hydroquinone, p-methoxyphenol, 2-tert-butylhydroquinone, and methylhydroquinone.
8. The tung oil-epoxy soybean oil-based aqueous polyurethane dispersion prepared by the preparation method according to any one of claims 1 to 7.