Polyurethane coating as well as preparation method and application thereof

Abstract

The invention discloses a polyurethane coating as well as a preparation method and application thereof. The invention relates to a polyurethane coating, which is prepared from the following raw materials according to the following solid-to-liquid ratio: a solvent, polyethylene glycol 2000, polycaprolactone glycol 2000, isophorone diisocyanate, a catalyst, a trans-4, 5-dihydroxy-1, 2-disulfane solution, an imidazolidinyl urea solution and a chain extender according to the solid-to-liquid ratio of (10 to 40): (1 to 2) g: (4 to 5) g: (1 to 5): (0.01 to 1): (5.20 to 7): (20 to 40): (2 to 10). The oil-water separation membrane prepared by adopting the polyurethane coating disclosed by the invention is a super-hydrophilic oil-water separation membrane, integrates strong adhesive force to a substrate, high mechanical property of a coating and dual protection and oil stain resistance, and can be used for large-scale long-term use of an oil-water separation material under severe conditions.

Description

Technical Field

[0001] This invention belongs to the field of new materials technology, and in particular relates to a polyurethane coating, its preparation method and application. Background Technology

[0002] Currently, methods for addressing oily wastewater pollution include gravity separation, mechanical recovery, centrifugation, in-situ combustion, chemical solidification, electrolysis, and bioremediation. However, these methods still suffer from limitations such as low separation efficiency, secondary pollution, high energy consumption, and high cost, significantly restricting their large-scale practical application. These methods typically produce limited oil-water separation performance, and the separation effect is incompatible with the requirements for reuse. Membrane separation materials with special wettability, due to their high separation efficiency, economic practicality, and simple operation, have gradually become one of the hot topics and directions in oil-water separation research both domestically and internationally, especially superhydrophilic oil-water separation membrane materials. Natural polymer materials and natural products are the most commonly used materials for constructing superhydrophilic surfaces. However, due to the instability and low durability of natural polymer coatings, and the fact that oily wastewater often has complex components such as corrosive substances and silt, natural polymer coatings often struggle to maintain long-term underwater superoleophobicity during oil-water separation, thus losing their oil-water separation capability. Therefore, preparing oil-water separation membrane materials with long-term stable and durable superhydrophilic-underwater superoleophobic coatings in a simple and economical manner remains a challenge.

[0003] To address this, Chinese invention patent CN106433437A, entitled "Method for Preparing Superhydrophobic and Superoleophilic Copper Mesh by Spraying," discloses a method for preparing superhydrophobic and superoleophilic copper mesh by spraying. The method involves mixing and reacting a polymeric polyol and a polyisocyanate, adding a hydrophilic chain extender and dibutyltin dilaurate, neutralizing the reaction with a neutralizing agent, adding amino silicone oil to obtain a prepolymer containing hydrophobic side chains, dispersing it in deionized water to obtain an aqueous polyurethane emulsion containing hydrophobic side groups, ultrasonically dispersing hydrophobic fumed silica nanoparticles in acetone, adding the aqueous polyurethane emulsion containing hydrophobic side groups to obtain a coating agent, spraying it onto the surface of the copper mesh, and drying to obtain a superhydrophobic / superoleophilic copper mesh. This invention offers good repairability, wear resistance, and acid and alkali resistance. Oil-water separators made from this copper mesh have significant advantages in separation efficiency and rate, and have broad market prospects. However, the prepared coating is a superhydrophobic coating, and superhydrophobic materials are difficult to use for long periods due to their low oil resistance. Summary of the Invention

[0004] The purpose of this invention is to provide a polyurethane coating, its preparation method, and its application.

[0005] To address the problems existing in the prior art, the technical solution adopted in this invention is: In a first aspect, the present invention provides a polyurethane coating composed of the following raw materials in the following solid-liquid ratio: Solvent: Polyethylene glycol 2000: Polycaprolactone diol 2000: Isophorone diisocyanate: Catalyst: trans-4,5-dihydroxy-1,2-dithioane solution: Imidazolidinyl urea solution: Chain extender = (10-40): (1-2): (4-5): (1-5): (0.01-1): (5-7): (20-40): (2-10); preferably 20:2:4:2.67:0.05:5.23:30.58:7.6.

[0006] Further, the trans-4,5-dihydroxy-1,2-disulfide solution is prepared by dissolving trans-4,5-dihydroxy-1,2-disulfide in N,N-dimethylformamide, wherein the mass ratio of trans-4,5-dihydroxy-1,2-disulfide to N,N-dimethylformamide in the trans-4,5-dihydroxy-1,2-disulfide solution is 0.2-2:5; The imidazolidinyl urea solution is prepared by dissolving imidazolidinyl urea in N,N-dimethylformamide, and the mass ratio of imidazolidinyl urea to N,N-dimethylformamide in the imidazolidinyl urea solution is 0.5-0.8:30.

[0007] Furthermore, the solvent is N,N-dimethylformamide; the catalyst is dibutyltin dilaurate; and the chain extender is prepared by dissolving tannic acid in N,N-dimethylformamide.

[0008] The mass ratio of tannic acid to N,N-dimethylformamide in the chain extender is 1-5:3-10, preferably 2.6:5.

[0009] Secondly, the present invention provides a method for preparing the polyurethane coating described in the first aspect, comprising the following steps: After adding polyethylene glycol 2000 and polycaprolactone glycol 2000 to the solvent and stirring evenly in an oil bath, isophorone diisocyanate and catalyst are added sequentially and stirred in an oil bath; then trans-4,5-dihydroxy-1,2-dithioane solution and imidazolidinyl urea solution are added and stirred in an oil bath for 1-5 hours; finally, chain extender is added and reacted in an oil bath to obtain polyurethane coating.

[0010] Furthermore, the temperature of the oil bath is 40-90℃.

[0011] Thirdly, the present invention provides the application of the polyurethane coating described in the first aspect above in the preparation of oil-water separation membranes.

[0012] Furthermore, the method for preparing the oil-water separation membrane includes the following steps: 1) Clean the substrate with ethanol and deionized water using ultrasonic cleaning, and then dry it in an oven; 2) Dilute the polyurethane coating described in the first aspect above; 3) Apply the diluted polyurethane coating evenly to the substrate surface and allow it to dry to obtain PUX@SSM; 4) PUX@SSM was stirred in an aqueous solution of 1,4-dithiothreitol to fully swell the polyurethane hydrogel coating, while reducing disulfide bonds to obtain thiol active sites. After the reaction was completed, the unreacted chemicals were washed away with deionized water. 5) Prepare a click reaction aqueous solution containing a photoinitiator and methacryloylethyl sulfobetaine, place PUX@SSM in the click reaction aqueous solution, and carry out a mercapto-alkenyl click reaction under ultraviolet light; 6) When the reaction is complete, rinse off the unreacted chemicals with deionized water to obtain SPUX@SSM.

[0013] Preferably, the substrate is a stainless steel mesh.

[0014] Further, the polyurethane coating described in the first aspect above is diluted to 10-30 wt% with DMF to obtain a polyurethane coating with a solid content of 1.7-5.1 wt%.

[0015] Furthermore, the concentration of the photoinitiator in the click reaction aqueous solution is 0.5-5 wt%, preferably 1 wt%; the concentration of the methacrylethyl sulfobetaine is 0.5-5 wt%, preferably 1 wt%. Introducing the above concentration of methacrylethyl sulfobetaine can increase the oil resistance of the coating surface.

[0016] Furthermore, the photoinitiator is a water-soluble photoinitiator suitable for 365nm ultraviolet light.

[0017] Furthermore, the photoinitiator is 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone or TPO-Li (lithium phosphate derivative).

[0018] The advantages and beneficial effects of this invention are: This invention uses tannic acid as a chain extender and adds imidazolidinyl urea to the long chain of the prepolymer, which enhances the chemical and physical crosslinking of the polyurethane hydrogel coating network, achieving a stable microphase separation structure between the soft and hard segments. Polyethylene glycol and polycaprolactone diol are used as soft segment components, with polyethylene glycol being hydrophilic and polycaprolactone diol being hydrophobic. The alternating hydrophilic and hydrophobic phases form a bicontinuous phase, further improving the mechanical properties of the polyurethane hydrogel coating. The addition of trans-4,5-dihydroxy-1,2-dithione to the long chain of the prepolymer provides active sites for the introduction of the zwitterionic substance methacryloylethyl sulfobetaine. The combination of the two is achieved through a thiol-ene click reaction, conveniently and quickly providing the coating with stronger oil resistance. The hydration capacity of the polyurethane hydrogel substrate and the hydration capacity of the SBMA zwitterionic brush structure synergistically construct a dual protective layer, giving the oil-water separation material superior oil resistance and improving its durability.

[0019] The polyurethane coating prepared by this invention is applied to a stainless steel mesh to form a superhydrophilic polyurethane coating. This coating combines the high mechanical properties of the polyurethane material with the antifouling properties of the superhydrophilic material. Furthermore, the polyurethane material is combined with the natural product tannic acid to reduce costs and energy consumption. This coating can be used for large-scale, long-term use of oil-water separation materials under harsh conditions.

[0020] This invention uses tannic acid, a natural polyphenol compound, as a chain extender to prepare a polyurethane coating. This can increase the chemical crosslinking of the polyurethane coating to improve its stability. The polyphenolic hydroxyl properties of tannic acid give it a mussel-like biomimetic function and stronger adhesion to various substrates, especially metal substrates.

[0021] The oil-water separation membrane prepared using the polyurethane coating of this invention is a superhydrophilic oil-water separation membrane that combines strong adhesion to the substrate, high mechanical properties of the coating itself, and dual protection against oil stains.

[0022] This invention utilizes a coating process to prepare oil-water separation membrane materials with a superhydrophilic coating. The coating offers advantages such as convenient storage and transportation, simple preparation process, applicability to various substrates, and reusability of the substrate after coating damage. Furthermore, it uses naturally derived tannic acid as one of the raw materials, reducing costs while improving the material's environmental friendliness. It has strong potential for large-scale industrial application. Attached Figure Description

[0023] Figure 1 The mechanical property test results for SPU1-SPU5 are shown in the figure. In the figure: a is the tensile mechanical property test of SPU1-SPU5 film samples, and b is the adhesion test of SPU2 coating to stainless steel substrate. Figure 2Infrared spectra of the polyurethane (PU2) coating prepared in Example 2, and the SPU1-SPU5 film prepared by grafting SBMA onto the PU1-5 coating; Figure 3 The figures show the experimental results of separation efficiency (SE) and separation flux (SF) in the oil-water separation performance test; in the figure: a is the experimental result of separation efficiency, and b is the experimental result of separation flux; among them, PU2@SSM is the one prepared in step 3) of Example 7; SPU1@SSM-SPU5@SSM are the oil-water separation membranes prepared in Examples 6-10, respectively; Figure 4 It is a polymeric structural formula. Detailed Implementation

[0024] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0025] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0026] Example 1

[0027] This embodiment provides a polyurethane (PUX) coating, the preparation method of which includes the following steps: 1) First, add 20g of DMF (N,N-dimethylformamide) to the flask as a solvent, then add 1g (0.5mmol) of polyethylene glycol 2000 (PEG) and 5g (2.5mmol) of polycaprolactone glycol 2000 (PCL). Stir well in an oil bath at 75℃. 2) Add 2.67g of isophorone diisocyanate (IPDI); 3) Add 0.05g of dibutyltin dilaurate (DBTDL) as a catalyst and stir in an oil bath at 75℃ for 1 hour; 4) Dissolve 0.23g of trans-4,5-dihydroxy-1,2-dithioethane (O-DTT) and 0.58g of imidazolidinyl urea (IU) in 5g of DMF and 30g of DMF respectively, add them to a flask, and stir in an oil bath at 75°C for 2 hours to form a long chain of prepolymer.

[0028] 5) 2.6g of tannic acid (TA) was dissolved in 5g of DMF and added to the flask as a chain extender. After reacting for 3 hours in an oil bath at 75°C, a PUX (X=1) coating with a solid content of about 17% was obtained.

[0029] like Figure 4 As shown in the figure, the most basic structural unit of the polyurethane coating is illustrated. Tannic acid acts as the polymer hub, its -OH groups reacting with the -NCO groups of IPDI to connect multiple long polyurethane chains. The orange spheres represent the polyphenolic hydroxyl arms of tannic acid, each arm containing five phenolic hydroxyl groups. Functional small molecules IU and O-DTT are added to the linear polyurethane chains. The -OH groups in IU and O-DTT react with the -NCO groups in IPDI to generate urethane groups. IU increases the physical crosslinking of the polymer, making it more robust, while O-DTT provides potential active sites for the introduction of SBMA. The SS bonds in O-DTT, after reduction by DTT, yield free -SH groups, which can be grafted onto SBMA via a click reaction. The soft portion consists of PEG and PCL, the ratio of which can be adjusted to give the polyurethane coating good hydrophilicity and mechanical properties.

[0030] Example 2

[0031] This embodiment provides a polyurethane (PUX) coating. The only difference between this embodiment and Example 1 is that 2g (1.0mmol) of polyethylene glycol 2000 (PEG) and 4g (2.0mmol) of polycaprolactone diol 2000 (PCL) are added in step 1. All other steps are the same as in Example 1, and a PUX (X=2) coating with a solid content of about 17% is prepared.

[0032] Comparative Example 1

[0033] This comparative example provides a polyurethane (PUX) coating. The only difference between this comparative example and Example 1 is that 3g (1.5mmol) of polyethylene glycol 2000 (PEG) and 3g (1.5mmol) of polycaprolactone diol 2000 (PCL) are added in step 1. All other steps are the same as in Example 1, and a PUX (X=3) coating with a solid content of about 17% is prepared.

[0034] Comparative Example 2

[0035] This comparative example provides a polyurethane (PUX) coating. The only difference between this comparative example and Example 1 is that 4g (2.0mmol) of polyethylene glycol 2000 (PEG) and 2g (1.0mmol) of polycaprolactone diol 2000 (PCL) are added in step 1. All other steps are the same as in Example 1, and a PUX (X=4) coating with a solid content of about 17% is prepared.

[0036] Comparative Example 3

[0037] This comparative example provides a polyurethane (PUX) coating. The only difference between this comparative example and Example 1 is that 5g (2.5mmol) of polyethylene glycol 2000 (PEG) and 1g (0.5mmol) of polycaprolactone diol 2000 (PCL) are added in step 1. All other steps are the same as in Example 1, and a PUX (X=5) coating with a solid content of about 17% is prepared.

[0038] Comparative Example 4

[0039] This comparative example provides a polyurethane coating. The only difference between this comparative example and Example 2 is that in step 4), trans-4,5-dihydroxy-1,2-dithionane was not added. Instead, 0.58g of imidazolidinyl urea (IU) was dissolved in 30g of DMF, added to a flask, and stirred in an oil bath at 75°C for 2 hours. All other steps are the same as in Example 2.

[0040] Comparative Example 5

[0041] This comparative example provides a polyurethane coating. The only difference between this comparative example and Example 2 is that in step 4), 1,4-butanediol is used instead of imidazolidinyl urea. All other aspects are the same as in Example 2.

[0042] Example 3 This embodiment provides an oil-water separation membrane (SPUX@SSM), the preparation method of which includes the following steps: 1) First, ultrasonically clean the SSM (stainless steel mesh) with ethanol and deionized water for 10 minutes each, and then dry it in an oven.

[0043] 2) The PUX coating prepared in Example 1 was diluted to 20 wt% with DMF to obtain a PUX coating with a solid content of 3.4%. The solid content of the PUX coating of 3.4% helps to improve the separation flux of the separation material.

[0044] 3) Then, the diluted PUX coating is evenly applied to the surface of the SSM and dried in an oven at 80°C to obtain PUX@SSM (X=1).

[0045] 4) PUX@SSM was stirred in a 10 mmol / L DTT (1,4-dithiothreitol) aqueous solution for 1 h to allow the polyurethane hydrogel coating to fully swell, while reducing disulfide bonds to obtain thiol active sites. After the reaction was completed, the unreacted chemicals were washed away with deionized water.

[0046] 5) Prepare an aqueous solution containing 1 wt% Darocur2959 (2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone) and 1 wt% SBMA (methacryloylethyl sulfobetaine). Place PUX@SSM in the above aqueous solution and heat at 365 nm (10 mW / cm). 2 Under ultraviolet light irradiation, each side of the separation membrane was irradiated for 5 minutes, and a mercapto-alkenyl click reaction was performed under ultraviolet light to graft SBMA onto the coating surface, wherein Darocur2959 was used as a photoinitiator. The introduction of SBMA improves the oil resistance of this invention.

[0047] 6) At the end of the reaction, wash away the unreacted chemicals with deionized water to obtain SPUX@SSM (X=1).

[0048] Example 4

[0049] This embodiment provides an oil-water separation membrane (SPUX@SSM) (X=2). The only difference between this embodiment and embodiment 3 is that step 2) uses the PUX coating prepared in embodiment 2, while the rest is the same as in embodiment 3.

[0050] Comparative Example 6 This comparative example provides an oil-water separation membrane (SPUX@SSM) (X=3). The only difference between this comparative example and Example 3 is that step 2) uses the PUX coating prepared in Comparative Example 1, while the rest are the same as in Example 3.

[0051] Comparative Example 7 This comparative example provides an oil-water separation membrane (SPUX@SSM) (X=4). The only difference between this comparative example and Example 3 is that step 2) uses the PUX coating prepared in Comparative Example 2, while the rest is the same as in Example 3.

[0052] Comparative Example 8 This comparative example provides an oil-water separation membrane (SPUX@SSM) (X=5). The only difference between this comparative example and Example 3 is that step 2) uses the PUX coating prepared in Comparative Example 3, while the rest are the same as in Example 3.

[0053] Comparative Example 9 This comparative example provides an oil-water separation membrane. The only difference between this comparative example and Example 4 is that step 2) uses the polyurethane coating prepared in Comparative Example 4, while the rest are the same as in Example 4.

[0054] Comparative Example 10 This comparative example provides an oil-water separation membrane. The only difference between this comparative example and Example 4 is that step 2) uses the polyurethane coating prepared in Comparative Example 5, while the rest are the same as in Example 4.

[0055] Comparative Example 11 This comparative example provides an oil-water separation membrane. The only difference between this comparative example and Example 4 is that in step 2), the PUX coating prepared in Example 2 is diluted to 5 wt% with DMF to obtain a PUX coating with a solid content of 0.85 wt%. All other steps are the same as in Example 4.

[0056] Comparative Example 12 This comparative example provides an oil-water separation membrane. The only difference between this comparative example and Example 4 is that: Step 2) Dilute the PUX coating prepared in Example 2 to 40 wt% with DMF to obtain a PUX coating with a solid content of 6.8 wt%. The rest is the same as in Example 4.

[0057] Experimental Example 1. Mechanical property testing Tensile mechanical property testing The PU1-PU5 coatings prepared in Examples 1-2 and Comparative Examples 1-3 were filled into polytetrafluoroethylene molds and dried to obtain PU1-PU5 films. SBMA was grafted onto the surface of the films according to steps 4)-6) of Example 3 to obtain SPU1-SPU5 films, and tensile dumbbell-shaped SPU1-SPU5 film samples with a size of 3*3cm were prepared. The coatings prepared in Comparative Examples 4 and 5 were filled into polytetrafluoroethylene molds and dried to obtain PUX films. SBMA was grafted onto the surface of the PUX films in the same manner to obtain polyurethane films, and 3*3cm tensile dumbbell-shaped polyurethane film samples were prepared.

[0058] The tensile mechanical properties of the above-mentioned membrane samples were tested using conventional methods by stretching dumbbell-shaped samples. The clamping distance of the samples was 30 mm, the stretching speed was 50 mm / min, and each sample was tested three times. The test results of SPU1-SPU5 membrane samples are as follows. Figure 1 As shown in Table 1, the test results of the polyurethane membrane samples prepared in Comparative Examples 4-5 are also shown.

[0059] like Figure 1 As shown in Figure a, comparing the stress-strain curves of SPU1-SPU5 with different PEG / PCL ratios, it can be seen that SPU2 with a PEG / PCL ratio of 1 / 2 exhibits the best tensile mechanical properties. Its tensile stress reaches 8 MPa, and its tensile strain reaches 868%.

[0060] Table 1: Tensile mechanical properties of polyurethane film samples prepared in Comparative Examples 4-5

[0061] A comparison of Comparative Example 4 with Examples 1 and 2 shows that Comparative Example 4, due to the absence of trans-4,5-dihydroxy-1,2-dithioane, significantly altered the distribution of soft and hard segments in the polyurethane, resulting in a decrease in tensile mechanical properties. A comparison of Comparative Example 5 with the Examples shows that Comparative Example 5, by using 1,4-butanediol instead of imidazolidinyl urea, changed the density of hydrogen bonds in the polyurethane, leading to a substantial decrease in tensile mechanical properties.

[0062] Adhesion performance test The adhesion of polyurethane film samples prepared by SPU1-SPU5 and Comparative Examples 4-5 to stainless steel substrates was tested using a pull-off adhesion tester (refer to GB / T5210-2006). For ease of testing, film coatings were prepared on the surface of the stainless steel plate. The preparation method was as follows: the polyurethane (PU1-PU5) coatings prepared in Examples 1-2 and Comparative Examples 1-3, and the coating prepared in Comparative Examples 4-5, were directly brushed onto the surface of the stainless steel plate to form a coating with a thickness of 0.1 mm. The spindle diameter used in the experiment was 10 mm. The coating failure mode was interfacial failure between the coating and the substrate. The average value was taken from four test points. The test results for SPU2 are as follows. Figure 1 b. The coating adhesion was 1.87 MPa. The coating adhesion of polyurethane film samples prepared by SPU1, SPU3-5 and Comparative Example 4-5 is shown in Table 2.

[0063] Table 2: Coating Adhesion

[0064] pass Figure 1 As shown in Table 2, among SPU1-SPU5, SPU2 has the best coating adhesion, with a coating adhesion of 1.87 MPa. The coating adhesion of Comparative Example 4 is only 0.7 MPa, and the coating adhesion of Comparative Example 5 is only 0.9 MPa.

[0065] Infrared spectroscopy analysis Figure 2 Infrared spectral analysis of the polyurethane (PU2) coating and SPU1-SPU5 films prepared in Example 2. Figure 2 As shown, 3361cm -1 The broad characteristic peaks are attributed to the presence of -OH and -NH groups, with -OH mainly originating from tannic acid and -NH mainly from urea groups, 2914 cm⁻¹. -1 The nearby characteristic peaks correspond to the asymmetric and symmetric stretching vibrations of the CH bond. From SPU1 to SPU5, 1725 cm⁻¹ -1 The characteristic peak of the ester group C=O bond and 1155 cm⁻¹ -1 The characteristic peak of the ester group CO bond at the 1078 cm⁻¹ continuously weakens, which is due to the reduction in the number of ester groups caused by the decrease in PCL components. From SPU1 to SPU5, the peak value is 1078 cm⁻¹.-1 The characteristic peaks of the COC bonds at the PEG content continuously intensify, which is due to the increase in ether bonds as the PEG component increases. Compared to PU2, SPU2 shows a stronger characteristic peak at 1030 cm⁻¹. -1 SO3 - The characteristic peaks of the groups were enhanced, which is attributed to the introduction of the zwitterionic brush of SBMA. Compared to PU2, SPU1-SPU5 showed enhanced peaks at 1605 cm⁻¹. -1 The presence of more pronounced C=C characteristic peaks at 1542 cm⁻¹ is due to the presence of sulfonic acid groups. The strong electron-withdrawing effect of sulfonic acid groups may influence the vibrational frequency of C=C in neighboring tannic acid through conjugation or induction, resulting in a higher peak at 1542 cm⁻¹. -1 The characteristic peak of some C=C bonds at this location has redshifted to 1605 cm⁻¹. -1 Place.

[0066] Oil-water separation performance test The separation performance of the PU2@SSM prepared in step 3) of Example 4, the oil-water separation membranes SPU1@SSM-SPU5@SSM prepared in Examples 3 and 4, the oil-water separation membranes prepared in Comparative Examples 6-8, and the oil-water separation membranes prepared in Comparative Examples 9-12 was measured.

[0067] 5.1 Test Method: Each group used two syringe plastic tubing and two metal long-tail clips to form an oil / water mixture separation device. The oil-water separation performance of six different oils (n-hexane, toluene, kerosene, diesel, gasoline, and petroleum ether) with deionized water was tested under gravity-driven conditions at room temperature. The oil-water separation membrane was thoroughly wetted with deionized water before use and then fixed between the two plastic tubing. All oil solvents were stained with Oil Red O. Different oil-water mixtures were prepared using 10g of oil and 10ml of water and poured into the device from the top of the tube. The separation efficiency (SE) and separation flux (SF) were calculated according to equations (1) and (2), respectively.

[0068] SE= M 1 / M 0 ×100% (1) SF= V / st (2) M 0 and M 1 The values ​​represent the weight (g) of the oil before and after separation, respectively. V Indicates the volume (ml) of water separated by the separation material; s and t The effective separation area (cm²) of the separating materials are respectively represented. 2 ) and the time (s) for oil-water separation.

[0069] like Figure 3 As shown in Figure a, the average separation efficiencies of PU2@SSM, SPU1@SSM, SPU2@SSM, SPU3@SSM, SPU4@SSM, and SPU5@SSM for the six oils were 98.42%, 99.02%, 99.07%, 99.07%, 99.15%, and 99.15%, respectively. Figure 3 As shown in b, the average separation flux is 39809 L·m -2 ·h -1 44593 L·m -2 ·h -1 50973 L·m -2 ·h -1 44593 L·m -2 ·h -1 50973 L·m -2 ·h -1 50973 L·m -2 ·h -1 It can be seen that, compared with PU2@SSM, SPU1@SSM-SPU5@SSM, which incorporate zwitterionic brushes, all exhibit superior separation efficiency for oil-water mixtures, demonstrating their stronger hydration capabilities. Furthermore, the latter has a higher separation flux, which may be due to the strong resistance to oil contamination preventing oil from polluting the surface of the separation material.

[0070] The separation performance of the oil-water separation membranes prepared in Comparative Examples 9-12 is shown in Table 3: Table 3: Separation performance of oil-water separation membranes prepared in Comparative Examples 5-8

[0071] By comparing Comparative Example 9 with the Example, it can be seen that Comparative Example 9 has reduced oil stain resistance because it does not have active sites for grafted SBMA ions.

[0072] By comparing Comparative Example 10 with the Example, it can be seen that Comparative Example 10 is difficult to withstand the scouring of oil-water mixtures due to the decrease in the mechanical properties of the coating.

[0073] By comparing Comparative Example 11 with the Example, it can be seen that the polyurethane hydrogel coating in Comparative Example 11 is too thin, resulting in a thinner coating and a decrease in hydration capacity.

[0074] By comparing Comparative Example 12 with the Example, it can be seen that the porosity of SSM in Comparative Example 12 decreased due to the excessive coating thickness, resulting in a significant decrease in separation flux.

[0075] The embodiments of this application have been described above with reference to the accompanying drawings. However, this application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. A polyurethane coating, characterized in that, Composed of the following raw materials in the following solid-liquid ratio: Solvent: Polyethylene glycol 2000: Polycaprolactone diol 2000: Isophorone diisocyanate: Catalyst: trans-4,5-dihydroxy-1,2-dithioethane solution: Imidazolidinyl urea solution: Chain extender = (10-40): (1-2): (4-5): (1-5): (0.01-1): (5-7): (20-40): (2-10); The trans-4,5-dihydroxy-1,2-dithione solution is prepared by dissolving trans-4,5-dihydroxy-1,2-dithione in a solvent, wherein the mass ratio of trans-4,5-dihydroxy-1,2-dithione to the solvent in the trans-4,5-dihydroxy-1,2-dithione solution is 0.2-2:

5. The imidazolidinyl urea solution is prepared by dissolving imidazolidinyl urea in a solvent, wherein the mass ratio of imidazolidinyl urea to solvent in the imidazolidinyl urea solution is 0.5-0.8:

30.

2. The polyurethane coating according to claim 1, characterized in that, Both the trans-4,5-dihydroxy-1,2-dithione solution and the imidazolidinyl urea solution use N,N-dimethylformamide as a solvent.

3. The polyurethane coating according to claim 1, characterized in that, The solvent is N,N-dimethylformamide; the catalyst is dibutyltin dilaurate; and the chain extender is prepared by dissolving tannic acid in N,N-dimethylformamide.

4. The polyurethane coating according to claim 3, characterized in that, The mass ratio of tannic acid to N,N-dimethylformamide in the chain extender is 1-5:3-10.

5. The method for preparing the polyurethane coating according to claim 1, characterized in that, Includes the following steps: Polyethylene glycol 2000 and polycaprolactone diol 2000 were added to a solvent and stirred evenly in an oil bath. Isophorone diisocyanate and a catalyst were added sequentially and stirred in an oil bath. Then, trans-4,5-dihydroxy-1,2-dithioane solution and imidazolidinyl urea solution were added and stirred in an oil bath for 1-5 hours. Finally, a chain extender was added and reacted in an oil bath to obtain a polyurethane coating.

6. The application of the polyurethane coating of claim 1 in the preparation of oil-water separation membranes.

7. The application according to claim 6, characterized in that, The method for preparing the oil-water separation membrane includes the following steps: 1) Clean the substrate with ethanol and deionized water using ultrasonic cleaning, and then dry it in an oven; 2) Dilute the polyurethane coating as described in claim 1; 3) Apply the diluted polyurethane coating evenly to the substrate surface and allow it to dry to obtain PUX@SSM; 4) PUX@SSM was stirred in an aqueous solution of 1,4-dithiothreitol to fully swell the polyurethane hydrogel coating, while reducing disulfide bonds to obtain thiol active sites. After the reaction was completed, the unreacted chemicals were washed away with deionized water. 5) Prepare a click reaction aqueous solution containing a photoinitiator and methacryloylethyl sulfobetaine, place PUX@SSM in the click reaction aqueous solution, and carry out a mercapto-alkenyl click reaction under ultraviolet light; 6) When the reaction is complete, rinse off the unreacted chemicals with deionized water to obtain SPUX@SSM.

8. The application according to claim 6, characterized in that, The polyurethane coating of claim 1 is diluted to 10-30 wt% with DMF to obtain a polyurethane coating with a solid content of 1.7-5.1 wt%.

9. The application according to claim 6, characterized in that, The photoinitiator is a water-soluble photoinitiator suitable for 365nm ultraviolet light.

10. The application according to claim 6, characterized in that, The concentrations of both the photoinitiator and methacryloylethyl sulfobetaine in the click reaction aqueous solution are 0.5-5 wt%.

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