A porous polyurethane foam, a method for producing the same, and use thereof

Abstract

The application belongs to the technical field of seawater desalination materials, and specifically discloses a porous polyurethane foam, a preparation method and application thereof. The porous polyurethane foam is a porous polymer material obtained by in-situ polymerization of a polymer solution containing polymerized monomers on the surface of a soluble porogen, and then dissolving out the soluble porogen to form pores. The polymerized monomers include aminoaniline trimer, polyethylene glycol and aliphatic diisocyanate trimer. The porous polyurethane foam has simple structure, good hydrophilicity, high water flux, excellent light-heat water evaporation performance, good salt resistance and easy preparation, and can be applied as an efficient interfacial solar seawater desalination material.

Description

Technical Field

[0001] This invention belongs to the field of seawater desalination materials technology, and specifically relates to a porous polyurethane foam, its preparation method and application. Background Technology

[0002] Seawater desalination is an effective way to solve the water pollution and water shortage crisis. Traditional seawater desalination methods include multi-stage flash distillation (MSF), multi-effect distillation (MED), reverse osmosis (RO), vapor pressure distillation (VCD), and electrochemical deposition. However, these methods suffer from high costs, the need for large-scale equipment, and unsuitability for remote areas. Therefore, seawater desalination technology utilizing environmentally friendly and widely available solar energy has received increasing attention. However, due to uncontrollable heat loss to the water body and low solar absorption rate, the energy utilization efficiency of traditional solar desalination technology is only 30-45%. In the past decade, interfacial solar seawater desalination materials have developed rapidly, directly and efficiently converting solar energy into heat energy and concentrating it at the air-water interface, greatly reducing heat loss and increasing the evaporation rate. Typical interfacial seawater desalination materials are designed with multi-layer structures, mainly including an evaporation layer, a water transport layer, and an insulation layer. However, their preparation is relatively complicated and carries the risk of debonding. Designing a multifunctional interfacial seawater desalination material presents a challenge. In addition, interfacial solar desalination materials suffer from salt accumulation, which hinders long-term continuous evaporation and requires regular cleaning, thus increasing costs. Therefore, it is necessary to design a salt-resistant desalination material to improve the application value of solar desalination technology.

[0003] On the other hand, preventing salt deposition while maintaining long-term stability and high evaporation efficiency is key to promoting the application of solar-powered seawater desalination technology, especially when desalinating high-concentration brine. Improving the salt resistance of materials is currently a major research hotspot. Current research on preventing salt deposition during evaporation mainly falls into two categories: functional separation of materials (Energy Environ.Sci., 2019, 12, 1840-1847; Advanced Energy Materials, 2018, 8, 1702884; Advanced Functional Materials, 2019, 29, 1905485) and increasing water flux (Energy Environ.Sci., 2018, 11, 1510-1519; Energy Environ.Sci., 2019, 12, 1558-1567). Separating the functional zones of the evaporation material can prevent salt from crystallizing in the evaporation zone. For example, controlling the flow of water can cause the material to flow to the non-evaporation zone where it crystallizes, or designing a hydrophilic-hydrophobic structure so that the hydrophilic layer transports water while the hydrophobic layer cuts off the transport of water to the evaporation surface, thereby preventing salt from crystallizing in the evaporation zone.

[0004] Existing technologies for improving the salt resistance of interfacial desalination materials often require complex multi-layered structures or additional auxiliary supports to separate functional zones, increasing costs. Methods using auxiliary water conveyance structures to accelerate water exchange also increase material complexity and pose a risk of debonding. Monolithic interfacial seawater desalination materials are mostly carbon-based evaporators (Advanced Energy Materials, 2018, 8, 1702149), wood-based carbonized evaporators (Energy Environ. Sci., 2021, 14, 5347-5357), or polymer-based evaporators (Solar Energy Materials and Solar Cells, 2020, 206, 110347). Most monolithic evaporators are prone to clogging during evaporation due to their small pore size (<10 μm), leading to reduced evaporation efficiency. Furthermore, polymer-based monolithic evaporators have low water flux and require additional treatment to improve hydrophilicity, making it difficult for the pure water evaporation rate to exceed 3 kg m³. -2 h -1 . Summary of the Invention

[0005] In view of the shortcomings of the prior art, the present invention provides a porous polyurethane foam, its preparation method and application. This material has a simple structure, good hydrophilicity, high water flux, excellent photothermal evaporation performance, good salt resistance and is easy to prepare, and can be used as a highly efficient interfacial solar seawater desalination material.

[0006] In a first aspect, the present invention provides a porous polyurethane foam, which is a porous polymer material obtained by in-situ polymerization of a polymer solution containing polymeric monomers on the surface of a soluble porogen, followed by dissolving the soluble porogen to form pores; the polymeric monomers include aminoaniline trimer, polyethylene glycol and aliphatic diisocyanate trimer.

[0007] Among the above monomers, aminoaniline trimer (ACAT) is the core photothermal functional component, providing the material with light absorption and photothermal conversion capabilities. The porous polymer material obtained by condensation of ACAT with polyethylene glycol and aliphatic diisocyanate trimer exhibits good hydrophilicity, capable of binding with water molecules through hydrogen bonds. Depending on the strength of these hydrogen bonds, the water in this porous polymer material can be classified into bound water, intermediate water, and free water (e.g., ...). Figure 9(As shown). Free water has a structure consisting of a water molecule and four surrounding water molecules bonded together by hydrogen bonds; bound water has a stable structure with strong interactions with the polymer chain; intermediate water lies between free water and bound water, combining with fewer water molecules through hydrogen bonds while having weaker interactions with the polymer chain. The presence of free water effectively reduces the enthalpy of evaporation. Furthermore, the material of this invention has a macroporous structure with a pore size of 50–100 μm, making it less prone to clogging. The porous structure transports water from the bottom to the surface through capillary action, and its hydrophilicity further improves water transport efficiency and enhances water evaporation performance. Simultaneously, by enabling rapid water exchange between the water body and the surface of the porous polymer material, the salt concentration on the material surface is maintained at a low level, thereby preventing the formation of crystallized salts. Therefore, the porous polymer material of this invention can effectively increase water flux, effectively activate water, reduce enthalpy of evaporation, increase evaporation rate, and improve salt tolerance.

[0008] According to a specific embodiment of the present invention, the molar ratio of aminoaniline trimer, polyethylene glycol, and aliphatic diisocyanate trimer in the polymerizing monomers is 1–6:1–4:1–3, preferably 1–2:1–2:1–2. The polymer obtained by polymerization under the above-defined monomer ratio has a more stable structure, better hydrophilicity and salt resistance, and also possesses efficient light absorption and photothermal conversion capabilities.

[0009] According to a specific embodiment of the present invention, the aliphatic diisocyanate trimer is a hexamethylene diisocyanate trimer.

[0010] According to a specific embodiment of the present invention, the polyethylene glycol is polyethylene glycol with a molecular weight of 400 to 5000, preferably PEG-400, PEG-600, PEG-800, PEG-1000, PEG-1500, and more preferably PEG-600.

[0011] According to a specific embodiment of the present invention, the soluble pore-forming agent is a water-soluble salt, preferably sodium chloride.

[0012] In a second aspect, the present invention provides a method for preparing the aforementioned porous polyurethane foam, comprising: filling soluble porogen particles into a mold to form a soluble porogen template; mixing polymer monomers, organic solvents and catalysts to form a polymer solution; adding the polymer solution to the soluble porogen template, heating to react, and then sequentially demolding, washing to remove the soluble porogen and drying the reaction product.

[0013] According to a specific embodiment of the present invention, the soluble pore-forming agent particles are salt particles; preferably, the particle size of the salt particles is less than 100 μm, more preferably 50 to 100 μm; preferably, the salt particles are sodium chloride particles.

[0014] According to a specific embodiment of the present invention, the organic solvent is selected from any one of N-methylpyrrolidone, tetrahydrofuran, or N,N-dimethylformamide, preferably N-methylpyrrolidone; the catalyst is organotin, preferably dibutyltin dilaurate; preferably, the mass fraction of the catalyst is 0.5-1% based on the total weight of the polymerizing monomers.

[0015] According to a specific embodiment of the present invention, the reaction proceeds according to the following procedure:

[0016] The reaction temperature is 50–70℃, preferably 70℃; the reaction time is 36–60 h, preferably 48 h.

[0017] The temperature is increased from 50–70°C to 150–170°C, preferably to 170°C, at a rate of 1–3°C / min, preferably 2°C / min.

[0018] The reaction temperature is 150–170℃, preferably 170℃; the reaction time is 1–3 h, preferably 2 h.

[0019] A third aspect of this invention provides the application of the aforementioned porous polyurethane foam in interfacial solar desalination materials or wastewater treatment materials. Tests have confirmed that the material of this invention has excellent desalination effects on seawater (salinity 3.5%) and wastewater, meeting WHO drinking water standards.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. The porous polyurethane foam provided by this invention, with aminoaniline trimer (ACAT) as the core photothermal functional component, is designed as a high-water-flux integral interfacial seawater desalination material. This promotes the development of solar-powered seawater desalination technology and provides new ideas for designing interfacial solar-powered seawater desalination materials with salt resistance and high evaporation efficiency.

[0022] 2. The porous polyurethane foam provided by this invention has a macroporous foam structure, good hydrophilicity, high water flux, good salt resistance, and excellent photothermal evaporation performance. It can be applied to interfacial solar seawater desalination and sewage treatment. It is a single component with a simple structure and can be reused after ultrasonic cleaning in deionized water.

[0023] 3. The preparation method provided by this invention has abundant raw material sources, can use various types of polyethylene glycol, is simple to prepare, and has low cost. For example, polyethylene glycol 600 (Bailingwei) costs about 376 RMB / 5kg, and hexamethylene diisocyanate trimer (Desmodur N 3600, Covestro) is commercialized and costs about 215 RMB / 1kg. Furthermore, the preparation method is simple, the solvents used in the preparation process have low toxicity, and the process parameters are easy to control. Attached Figure Description

[0024] Figure 1 Infrared spectrum;

[0025] Figure 2 This is a scanning electron microscope image;

[0026] Figure 3 This describes the change of contact angle over time.

[0027] Figure 4 The results are from water flux tests.

[0028] Figure 5 The results are from the evaporation rate test.

[0029] Figure 6 For seawater desalination effect;

[0030] Figure 7 For the purpose of wastewater desalination;

[0031] Figure 8 The results of the salt resistance test;

[0032] Figure 9 This is a schematic diagram showing the state of water in a porous polymer material. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] Example 1: Preparation of porous polyurethane foam for interfacial solar seawater desalination

[0035] 1. Preparation of salt template: Grind the dried NaCl particles three times with a grinder, then sieve them through a 150-mesh stainless steel sieve. The sieved NaCl particles are then sieved a second time through a 300-mesh stainless steel sieve to obtain NaCl particles with a size range of 50-100μm. Spread petroleum jelly evenly in a 10×10×2mm polytetrafluoroethylene mold, and fill the mold with NaCl particles to obtain the required salt template.

[0036] 2. Preparation of polymer solution: In a round-bottom flask, 1 mmol of aminoaniline trimer, 1 mmol of hexamethylene diisocyanate trimer and 1 mmol of polyethylene glycol 600 were dissolved in 4 mL of N-methylpyrrolidone. After stirring evenly, dibutyltin dilaurate (1 wt%) was added dropwise and stirred at room temperature for 60 s to obtain polymer solution.

[0037] 3. Preparation of porous polyurethane foam: The polymer solution was added to a salt template, and the reaction procedure was as follows: 1) Reaction at 70℃ for 48 hours; 2) Heating to 70-170℃ for 1 hour; 3) Curing at 170℃ for 2 hours. After demolding with petrolatum, the product was ultrasonically cleaned three times with deionized water and dried to obtain the target porous polyurethane foam. The reaction formula is as follows:

[0038]

[0039] Example 2: Preparation of porous polyurethane foam for interfacial solar seawater desalination

[0040] 1. Preparation of salt template: Grind the dried NaCl particles three times with a grinder, and then sieve them through a 300-mesh stainless steel sieve to obtain NaCl particles with a size range of 50-100μm. Spread Vaseline evenly in a polytetrafluoroethylene mold with a size of 30×30×2mm, and fill the mold with NaCl particles to obtain the required salt template.

[0041] 2. Preparation of polymer solution: In a round-bottom flask, 2 mmol of aminoaniline trimer, 3 mmol of hexamethylene diisocyanate trimer and 2 mmol of polyethylene glycol 400 were dissolved in 8 mL of N-methylpyrrolidone. After stirring evenly, dibutyltin dilaurate (1 wt%) was added dropwise and stirred at room temperature for 60 s to obtain polymer solution.

[0042] 3. Preparation of porous polyurethane foam: The polymer solution was added to the salt template, and the reaction procedure was as follows: 1) Reaction at 70℃ for 48 hours; 2) Heating at 70~170℃ for 1 hour; 3) Curing at 170℃ for 2 hours. After demolding with petrolatum, the product was ultrasonically cleaned three times with deionized water and dried to obtain the target porous polyurethane foam.

[0043] Taking the porous polyurethane foam prepared in Example 1 as an example, the following experimental studies were conducted.

[0044] I. Structural Determination: Infrared spectroscopy was used to characterize the polymer and determine its functional groups. The infrared spectrum is shown below. Figure 1As shown, the solid line represents aniline trimer (ACAT), and the dashed line represents the polymer obtained by reacting aniline trimer, hexamethylene diisocyanate trimer, and polyethylene glycol 600. New characteristic peaks such as OH, -CH2-, C=O, arC=C, and COC can be seen.

[0045] II. Microstructure Scanning: The porous polyurethane foam was immersed in liquid nitrogen for five minutes, then the brittle fracture surface was removed. The microstructure of the brittle fracture surface under a cold field emission scanning electron microscope is shown below. Figure 2 As shown.

[0046] III. Contact Angle Test: The change in contact angle over time is measured to characterize its hydrophilic properties. To ignore the influence of gravity, a 2μL water droplet is placed on the sample surface, and the change in the droplet profile is recorded via video. The process of contact angle change over time is as follows: Figure 3 As shown.

[0047] IV. Water Flux Test: Completely dried porous polyurethane foam was immersed in deionized water, and its mass was measured every minute until it remained constant for 20 consecutive minutes (Δm < 0.01 g). During weighing, the sample was placed in a reagent bottle, and its surface moisture was quickly wiped dry with filter paper before each weighing. It exhibits a high water flux (14.4 L / m²). -2 h -1 The maximum water content can reach 2.86 g / cm³. -1 Water transport capacity such as Figure 4 As shown.

[0048] V. Evaporation Rate Test: A 10×10×30mm cuvette was used as the evaporation container and placed in expandable polystyrene (EPS) foam for insulation. The cuvette was filled with water, and then porous polyurethane foam from Example 1 was placed at the air-water interface. After the light source stabilized, a VISI-Standard standard connected to a multimeter was used to quantitatively measure and adjust the solar intensity. Subsequently, the mouth of the cuvette was placed at the center of the light source. The mass change of water was measured using an electronic horizon connected to a computer. Data was collected every minute using a METTLER TOLEDO SerialPortToKeyboard, with each test lasting one hour, to obtain the evaporation rate under different solar radiation. When solar energy was the sole input energy source, the evaporation rate was measured under different solar intensities (0.5 sun, 0.5 kW m³ / s). -2 ;1 sun, 1 kW m -2 ;2sun,2kW m -2 The evaporation rate and evaporation efficiency of pure water are as follows: Figure 5 As shown. Under 1 solar intensity, 3.47 kg m can be achieved. -2 h -1 It has a high evaporation rate and a high evaporation efficiency of 94.3%.

[0049] VI. Seawater desalination effect under one solar radiation intensity: Seawater (salinity 3.5%) and ordinary ionic solution (Na+) were used. + ,K + Ca 2+ ,and Mg 2+ The condensate was collected and the ion concentration was detected by inductively coupled plasma mass spectrometry (ICP-MS). It exhibits excellent desalination effects on seawater (salinity 3.5%) and wastewater, meeting WHO drinking water standards, such as... Figures 6-7 As shown.

[0050] VII. Salt Resistance Test: A sufficient amount of sodium chloride (33 wt%) was applied to the surface of the porous polyurethane foam from Example 1, and then it was placed in seawater (salinity 3.5%) and continuously irradiated under one solar intensity. Surface changes of the evaporator were recorded every 15 minutes. It exhibited good salt resistance; in seawater, sufficient NaCl (33 wt%) was removed after 75 minutes. Figure 8 As shown.

[0051] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

Claims

1. A porous polyurethane foam, characterized in that, It is a porous polymer material obtained by in-situ polymerization of a polymer solution containing polymer monomers on the surface of a soluble porogen, followed by dissolving the soluble porogen to form pores. The polymer monomers include aminoaniline trimer, polyethylene glycol and aliphatic diisocyanate trimer, and the molar ratio of aminoaniline trimer, polyethylene glycol and aliphatic diisocyanate trimer is 1~6:1~4:1~3; The structural formula of the aminoaniline trimer is: 。 2. The porous polyurethane foam according to claim 1, characterized in that, In the polymer monomers, the molar ratio of aminoaniline trimer, polyethylene glycol and aliphatic diisocyanate trimer is 1~2:1~2:1~2.

3. The porous polyurethane foam according to claim 1, characterized in that, The aliphatic diisocyanate trimer is a hexamethylene diisocyanate trimer.

4. The porous polyurethane foam according to claim 1, characterized in that, The polyethylene glycol is polyethylene glycol with a molecular weight of 400 to 5000.

5. The porous polyurethane foam according to claim 4, characterized in that, The polyethylene glycol is PEG-400, PEG-600, PEG-800, PEG-1000, or PEG-1500.

6. The porous polyurethane foam according to claim 5, characterized in that, The polyethylene glycol is PEG-600.

7. The porous polyurethane foam according to claim 1, characterized in that, The soluble porogen is a water-soluble salt.

8. The porous polyurethane foam according to claim 7, characterized in that, The soluble porogen is sodium chloride.

9. A method for preparing porous polyurethane foam according to any one of claims 1 to 8, characterized in that, The preparation method includes: Soluble porogen particles are filled into a mold to form a soluble porogen template; A polymer solution is prepared by mixing monomers, organic solvents, and catalysts. The polymer solution is added to a soluble porogen template, heated to induce a reaction, and then the reaction product is sequentially demolded, washed to remove the soluble porogen, and dried.

10. The preparation method according to claim 9, characterized in that, The soluble porogen particles are salt particles with a particle size of 50~100 μm.

11. The preparation method according to claim 10, characterized in that, The salt particles are sodium chloride particles.

12. The preparation method according to claim 9, characterized in that, The organic solvent is selected from any one of N-methylpyrrolidone, tetrahydrofuran, or N,N-dimethylformamide; the catalyst is organotin; and the mass fraction of the catalyst is 0.5-1% based on the total weight of the monomers.

13. The preparation method according to claim 12, characterized in that, The organic solvent is N-methylpyrrolidone; the catalyst is dibutyltin dilaurate.

14. The preparation method according to claim 9, characterized in that, The reaction is carried out according to the following procedure: The reaction temperature is 50~70 ℃, and the reaction time is 36~60 h; The reaction temperature was increased from 50~70 ℃ to 150~170 ℃ at a rate of 1~3 ℃ / min, and the reaction time was 1~3 h.

15. The preparation method according to claim 14, characterized in that, The reaction is carried out according to the following procedure: The reaction temperature was 70 °C, and the reaction time was 48 h. The reaction temperature was increased from 70 °C to 170 °C at a rate of 2 °C / min, and the reaction time was 2 h.

16. The application of the porous polyurethane foam according to any one of claims 1 to 8 in interfacial solar desalination materials or wastewater treatment materials.

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