A modified polyurethane gas separation membrane and its preparation method

Abstract

This invention discloses a modified polyurethane gas separation membrane and its preparation method, belonging to the field of membrane separation technology. The modified polyurethane gas separation membrane of this invention comprises polyurethane soft segments and fluorinated hard segments; the polyurethane soft segments are composed of oligomeric diols, and the fluorinated hard segments are composed of a fluorinated chain extender and an isocyanate; the fluorinated chain extender refers to a fluorinated chain extender having two fluorinated alkyl side chains. The fluorinated polyurethane gas separation membrane prepared by this invention has the characteristics of high permeability and good separation selectivity, and is suitable for CO2 separation.

Description

Technical Field

[0001] This invention relates to the field of membrane separation technology, and in particular to a modified polyurethane gas separation membrane and its preparation method. Background Technology

[0002] Global warming is one of the world's major environmental concerns, and the massive emission of CO2 is the primary cause of the greenhouse effect and global climate change. Developing efficient and rapid CO2 separation technologies is of paramount importance to the global environment and economy. Common CO2 separation technologies include absorption, adsorption, cryogenic distillation, and membrane separation. Membrane separation technology, with its advantages of simple operation, high efficiency, low energy consumption, and small footprint, is one of the most environmentally friendly technologies currently available and shows great promise for application in the field of CO2 separation.

[0003] The core of gas membrane separation is the membrane material, and the correct selection of the membrane material is crucial, as it determines the final gas separation performance of the prepared gas separation membrane. Polysulfone, polycarbonate, polyimide, Pebax, and polyurethane (PU) are commonly used polymer materials for gas separation. PU is widely used in gas separation due to its good thermal stability and ideal permeation properties. It consists of hard segments (diisocyanate and chain extender) and soft segments, and the gas separation performance of PU membranes can be improved by adjusting the monomer ratio, membrane preparation process, and phase separation.

[0004] Compared to non-fluorinated polymers, polymers with fluorinated groups exhibit significant improvements in various aspects, such as low dielectric constant, high thermal stability, flame retardancy, and higher gas permeability. Fluorinated polymers also exhibit excellent permeability and selectivity, and are often used for CO2 separation. Hollander et al. prepared a high-strength but poor-flexible FPU using fluorinated isocyanate (C6F4(OCN)2); Turri et al. prepared an FPU using fluorinated polyether diol (ZDOL) and isophorone diisocyanate (IPDI), which had low surface tension and acid resistance, but the dynamic mechanical properties of the material decreased due to imperfect internal microphase separation; Tang et al. prepared an FPU using a fluorinated end-capping agent, which has the advantages of low surface energy and water resistance, but the fluorine content introduced as an end-capping agent was very low, and had little impact on the performance of the modified polyurethane. In addition, organic fluorine monomers are expensive, and blindly increasing their dosage simply to enhance the modification effect would increase costs and prevent industrial applications. Therefore, it is of great significance to effectively utilize organofluorine modified polyurethane to improve its gas permeability without significantly increasing costs. Since side chains in polymers are more reactive than the main chain, the introduction of fluorinated side chains has a more pronounced impact on the performance of gas separation membranes. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a modified polyurethane gas separation membrane and its preparation method. This invention modifies polyurethane by synthesizing a fluorinated chain extender, and simultaneously provides a method for preparing a fluorinated polyurethane gas separation membrane. The resulting fluorinated polyurethane gas separation membrane exhibits high permeability and good separation selectivity, making it suitable for CO2 separation.

[0006] The technical solution of the present invention is as follows:

[0007] One object of the present invention is to provide a modified polyurethane gas separation membrane, comprising a polyurethane soft segment and a fluorinated hard segment; wherein the polyurethane soft segment is composed of an oligomeric diol, and the fluorinated hard segment is composed of a fluorinated chain extender and an isocyanate; wherein the fluorinated chain extender is a fluorinated chain extender containing two fluorinated alkyl side chains obtained by an addition reaction on a 2-amino-1,3-propanediol segment.

[0008] Further, by mass parts, the raw materials of the modified polyurethane gas separation membrane include the following components: 3-7 parts of fluorinated chain extender; 20-40 parts of oligomeric diol; 5-10 parts of diisocyanate; 1-2 parts of catalyst; and 100-120 parts of solvent.

[0009] Furthermore, the fluorinated chain extender is synthesized by reacting fluorinated methacrylate with 2-amino-1,3-propanediol.

[0010] Furthermore, the fluorinated chain extender is obtained by reacting fluorinated methacrylate with 2-amino-1,3-propanediol, washing with water, and then distilling under reduced pressure.

[0011] Further, by mass percentage, the fluorinated chain extender comprises the following components: 40-60 parts of fluorinated methacrylate; 5-8 parts of 2-amino-1,3-propanediol; and 60-80 parts of ethanol.

[0012] Furthermore, the fluorinated methacrylate is trifluoroethyl methacrylate, pentafluoropropyl methacrylate, hexafluorobutyl methacrylate, nonafluorohexyl methacrylate, dodecafluoroheptyl methacrylate, or heptadecafluorodecyl methacrylate.

[0013] Further, the oligomeric diol is one or more of hydroxyl-terminated polybutadiene, polytetramethylene glycol, polycaprolactone diol, polypropylene glycol, and poly(1,4-butanediol adipate); the diisocyanate is isophorone diisocyanate, hexamethylene diisocyanate, 4,4'-diisocyanate diphenylmethane, toluene-2,4-diisocyanate, or 1,5-naphthalene diisocyanate; and the solvent is one of tetrahydrofuran, acetone, butanone, ethyl acetate, dimethylformamide, and dimethylacetamide.

[0014] Furthermore, the catalyst is a mixed solution of dibutyltin dilaurate and tetrahydrofuran, wherein the concentration of dibutyltin dilaurate in the catalyst is 0.5–2 wt%.

[0015] Further, the catalyst is a mixed solution of dibutyltin dilaurate and tetrahydrofuran, wherein the concentration of dibutyltin dilaurate in the catalyst is 0.5wt%, 0.8wt%, 1.0wt%, 1.5wt%, or 2wt%.

[0016] In one embodiment of the present invention, the concentration of dibutyltin dilaurate in the catalyst is 1.0 wt%.

[0017] Furthermore, the thickness of the modified polyurethane gas separation membrane is 30–200 μm.

[0018] Another object of the present invention is to provide a method for preparing the above-mentioned modified polyurethane gas separation membrane, comprising the following steps, in parts by mass:

[0019] S1: Preparation of fluorinated chain extender: Add 60-80 parts of ethanol to 40-60 parts of fluorinated methacrylate and 5-8 parts of 2-amino-1,3-propanediol, mix and react to obtain a crude product. After washing with water, distill under reduced pressure to obtain a yellow viscous liquid, which is the fluorinated chain extender solution. The equation for the above reaction is as follows:

[0020]

[0021] Where: R f These are alkyl side chains with different numbers of fluorine atoms.

[0022] S2: Preparation of casting solution: Mix 20-40 parts of oligomeric diol with 5-10 parts of diisocyanate, add 1-2 parts of catalyst and 100-120 parts of solvent, stir to obtain a prepolymer, then add 3-7 parts of the fluorinated chain extender prepared in step S1, and after reaction, obtain a polyurethane casting solution; the reaction equation is as follows:

[0023]

[0024] S3: After the casting solution obtained in S2 is allowed to stand to remove bubbles, it is spread evenly on a tetrafluoroethylene plate, allowed to stand again for 10-15 hours to remove solvent, and then dried to obtain a modified polyurethane gas separation membrane.

[0025] Furthermore, in step S1, the temperature of the mixing reaction is 60-65°C, and the time is 4-6 hours;

[0026] As an embodiment of the present invention, in step S1, the temperature of the mixing reaction is 60°C, 62°C or 65°C, and the time is 4h, 5h or 6h.

[0027] Furthermore, in step S2, the stirring temperature is 30–40°C, and the stirring time is 3–6 h; the chain extension reaction time is 1–4 h.

[0028] As an embodiment of the present invention, in step S2, the stirring temperature is 30°C, 35°C or 40°C, and the time is 3h, 4h, 5h or 6h; the chain extension reaction time is 1h, 2h, 3h or 4h.

[0029] Furthermore, in step S3, the time for static degassing is 2-3 hours; the drying temperature is 40-100℃ and the time is 24 hours.

[0030] As an embodiment of the present invention, in step S3, the time for static degassing is 2h, 2.2h, 2.5h or 3h; the drying temperature is 40℃, 50℃, 60℃, 80℃ or 100℃, and the time is 24h.

[0031] One of the modified polyurethane gas separation membranes can be used to capture CO2 from flue gas.

[0032] The flue gas is a mixture of gases and soot, containing carbon dioxide, nitrogen, and other gases.

[0033] The beneficial technical effects of this invention are as follows:

[0034] (1) This invention provides a method for preparing a fluorinated polyurethane gas separation membrane from the perspective of polyurethane chain extenders. By performing a Michael addition reaction between fluorinated methacrylate and the primary amine hydrogen in 2-amino-1,3-propanediol, two fluorinated alkyl side chains are introduced onto the diol chain extender. The preparation and introduction of the bi-sided fluorinated alkyl chain extender improves the membrane's permeability to CO2 molecules and its CO2 / N2 selectivity, further enhancing gas separation performance. Compared to polyurethanes with a single-sided fluorinated chain and perfluoroalcohol end caps, this invention significantly increases the fluorine content in the prepared polyurethane without increasing production costs. Furthermore, the soft segments of the fluorinated polyurethane in this invention are composed of oligomeric diols, providing flexibility to the polyurethane membrane and facilitating gas molecule permeation; the hard segments are composed of fluorinated chain extenders and isocyanates, ensuring the polymer's film-forming properties, providing mechanical properties to the polyurethane membrane, and improving the stability of the membrane structure.

[0035] (2) The preparation process of this invention is simple, the production cost is low, the raw materials are readily available, the film formation process is easy to control and the film formation is good. At the same time, the gas separation membrane prepared has the advantages of strong flexibility, large permeation flux, high gas selectivity, and stable structure and performance, and is suitable for CO2 separation. Attached Figure Description

[0036] Figure 1This is a chemical structure diagram of the modified polyurethane gas separation membrane of the present invention.

[0037] In the diagram: R f These are alkyl side chains with different numbers of fluorine atoms.

[0038] Figure 2 The infrared spectrum of the fluorinated chain extender of Example 1 of the present invention is shown.

[0039] Figure 3 The image shows the infrared spectrum of the modified polyurethane film of Example 1 of this invention.

[0040] Figure 4 This is a surface SEM image of the modified polyurethane film of Example 1 of the present invention. Detailed Implementation

[0041] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0042] This invention provides a method for preparing a modified polyurethane gas separation membrane from the perspective of polyurethane chain extenders. The introduction of fluorinated chain extenders increases the stiffness and free volume of the polyurethane chains, leading to increased gas permeability. The membrane produced by this invention exhibits high gas permeability and good separation selectivity. The method is characterized by its simple process, low production cost, excellent membrane separation performance, and good mechanical properties.

[0043] In the gas separation membrane prepared by this invention, the fluoroalkyl chains of the fluorinated polyurethane migrate to the membrane surface due to their similar polarity to air. There is a strong quadrupole-dipole interaction between CO2 molecules and the fluoroalkyl chains. Therefore, during gas dissolution and diffusion, the membrane surface can adsorb more CO2 molecules. The introduced fluoroalkyl chains interact with CO2, causing CO2 molecules to dissolve rapidly within the membrane. Since the fluoroalkyl chains do not have a quadrupole-dipole interaction with N2, this enhances gas permeability and selectivity. Furthermore, the presence of the fluoroalkyl chains gives the membrane segments a larger free volume, accelerating the diffusion process of CO2 molecules and further improving CO2 permeability. Therefore, this invention, through the preparation and introduction of bilateral fluoroalkyl chain extenders, improves the membrane's permeability to CO2 molecules and CO2 / N2 selectivity, further enhancing gas separation efficiency.

[0044] The following specific embodiments further illustrate the solution of the present invention. However, the following embodiments are only explanations of the present invention and are not intended to limit the present invention. Any solution within the scope of the present invention is within the protection scope of the present invention.

[0045] Example 1

[0046] The modified polyurethane gas separation membrane is prepared by the following steps:

[0047] (1) Preparation of fluorinated chain extender: 40 parts of dodecafluoroheptyl methacrylate and 5 parts of 2-amino-1,3-propanediol were added to a three-necked flask, and 60 parts of ethanol were added as solvent. The reaction was carried out at 60°C for 4 hours. The crude product was washed with deionized water to remove the solvent, and finally a yellow viscous liquid was obtained by vacuum distillation.

[0048] (2) Preparation of casting solution: 20 parts of hydroxyl-terminated polybutadiene and 5 parts of isophorone diisocyanate were mixed, and 1 part of catalyst (the catalyst was a mixed solution of dibutyltin dilaurate and tetrahydrofuran, the concentration of dibutyltin dilaurate in the catalyst was 1 wt%) and 100 parts of tetrahydrofuran were added. The mixture was stirred thoroughly at 40°C for 6 h to form a prepolymer. 3 parts of the fluorinated chain extender prepared in step (1) were added, and the reaction was carried out for 1 h to obtain the polyurethane casting solution.

[0049] (3) Preparation of polyurethane membrane: The casting solution obtained in step (2) was allowed to stand for 3 hours to remove bubbles. The casting solution was then spread on a clean tetrafluoroethylene plate and allowed to stand at room temperature for 12 hours to remove the solvent. The membrane was then dried in an oven at 60°C for 24 hours to obtain a fluorinated polyurethane gas separation membrane. The thickness of the membrane was measured to be 76 μm.

[0050] Example 2

[0051] The modified polyurethane gas separation membrane is prepared by the following steps:

[0052] (1) Preparation of fluorinated chain extender: 40 parts of dodecafluoroheptyl methacrylate and 5 parts of 2-amino-1,3-propanediol were added to a three-necked flask, and 60 parts of ethanol were added as solvent. The reaction was carried out at 60°C for 4 hours. The crude product was washed with deionized water to remove the solvent, and finally a yellow viscous liquid was obtained by vacuum distillation.

[0053] (2) Preparation of casting solution: 25 parts of hydroxyl-terminated polybutadiene and 6 parts of isophorone diisocyanate were mixed, and 1 part of catalyst (the catalyst was a mixed solution of dibutyltin dilaurate and tetrahydrofuran, the concentration of dibutyltin dilaurate in the catalyst was 1 wt%) and 100 parts of tetrahydrofuran were added. The mixture was stirred thoroughly at 40°C for 6 h to form a prepolymer. 4 parts of the fluorinated chain extender prepared in step (1) were added, and the mixture was reacted for 2 h to obtain the polyurethane casting solution.

[0054] (3) Preparation of polyurethane membrane: The casting solution obtained in step (2) was allowed to stand for 3 hours to remove bubbles. The casting solution was then spread on a clean tetrafluoroethylene plate and allowed to stand at room temperature for 12 hours to remove the solvent. The membrane was then dried in an oven at 60°C for 24 hours to obtain a fluorinated polyurethane gas separation membrane. The thickness of the membrane was measured to be 82 μm.

[0055] Example 3

[0056] The modified polyurethane gas separation membrane is prepared by the following steps:

[0057] (1) Preparation of fluorinated chain extender: 40 parts of dodecafluoroheptyl methacrylate and 5 parts of 2-amino-1,3-propanediol were added to a three-necked flask, and 70 parts of ethanol were added as solvent. The reaction was carried out at 60°C for 4 hours. The crude product was washed with deionized water to remove the solvent, and finally a yellow viscous liquid was obtained by vacuum distillation.

[0058] (2) Preparation of casting solution: 30 parts of hydroxyl-terminated polybutadiene and 6 parts of isophorone diisocyanate were mixed, and 1 part of catalyst (the catalyst was a mixed solution of dibutyltin dilaurate and tetrahydrofuran, the concentration of dibutyltin dilaurate in the catalyst was 1 wt%) and 100 parts of tetrahydrofuran were added. The mixture was stirred thoroughly at 40°C for 6 h to form a prepolymer. 5 parts of the fluorinated chain extender prepared in step (1) were added, and the reaction was carried out for 2 h to obtain the polyurethane casting solution.

[0059] (3) Preparation of polyurethane membrane: The casting solution obtained in step (2) was allowed to stand for 3 hours to remove bubbles. The casting solution was then spread on a clean tetrafluoroethylene plate and allowed to stand at room temperature for 12 hours to remove the solvent. The membrane was then dried in an oven at 60°C for 24 hours to obtain a fluorinated polyurethane gas separation membrane. The thickness of the membrane was measured to be 79 μm.

[0060] Example 4

[0061] The modified polyurethane gas separation membrane is prepared by the following steps:

[0062] (1) Preparation of fluorinated chain extender: 40 parts of dodecafluoroheptyl methacrylate and 5 parts of 2-amino-1,3-propanediol were added to a three-necked flask, and 70 parts of ethanol were added as solvent. The reaction was carried out at 60°C for 4 hours. The crude product was washed with deionized water to remove the solvent, and finally a yellow viscous liquid was obtained by vacuum distillation.

[0063] (2) Preparation of casting solution: 35 parts of hydroxyl-terminated polybutadiene and 6 parts of isophorone diisocyanate were mixed, and 1 part of catalyst (the catalyst was a mixed solution of dibutyltin dilaurate and tetrahydrofuran, the concentration of dibutyltin dilaurate in the catalyst was 1 wt%) and 100 parts of tetrahydrofuran were added. The mixture was stirred thoroughly at 40°C for 6 h to form a prepolymer. 6 parts of the fluorinated chain extender prepared in step (1) were added, and the reaction was carried out for 3 h to obtain the polyurethane casting solution.

[0064] (3) Preparation of polyurethane membrane: The casting solution obtained in step (2) was allowed to stand for 3 hours to remove bubbles. The casting solution was then spread on a clean tetrafluoroethylene plate and allowed to stand at room temperature for 12 hours to remove the solvent. The membrane was then dried in an oven at 60°C for 24 hours to obtain a fluorinated polyurethane gas separation membrane. The thickness of the membrane was measured to be 93 μm.

[0065] Example 5

[0066] The modified polyurethane gas separation membrane is prepared by the following steps:

[0067] (1) Preparation of fluorinated chain extender: 40 parts of dodecafluoroheptyl methacrylate and 5 parts of 2-amino-1,3-propanediol were added to a three-necked flask, and 80 parts of ethanol were added as solvent. The reaction was carried out at 60°C for 4 hours. The crude product was washed with deionized water to remove the solvent, and finally a yellow viscous liquid was obtained by vacuum distillation.

[0068] (2) Preparation of casting solution: 40 parts of hydroxyl-terminated polybutadiene and 10 parts of isophorone diisocyanate were mixed, and 1 part of catalyst (the catalyst was a mixed solution of dibutyltin dilaurate and tetrahydrofuran, the concentration of dibutyltin dilaurate in the catalyst was 1 wt%) and 100 parts of tetrahydrofuran were added. The mixture was stirred thoroughly at 40°C for 6 h to form a prepolymer. 7 parts of the fluorinated chain extender prepared in step (1) were added, and the reaction was carried out for 4 h to obtain the polyurethane casting solution.

[0069] (3) Preparation of polyurethane membrane: The casting solution obtained in step (2) was allowed to stand for 3 hours to remove bubbles. The casting solution was then spread on a clean tetrafluoroethylene plate and allowed to stand at room temperature for 12 hours to remove the solvent. The membrane was then dried in an oven at 60°C for 24 hours to obtain a fluorinated polyurethane gas separation membrane. The thickness of the membrane was measured to be 86 μm.

[0070] Example 6

[0071] The modified polyurethane gas separation membrane is prepared by the following steps:

[0072] (1) Preparation of fluorinated chain extender: 50 parts of trifluoroethyl methacrylate and 6 parts of 2-amino-1,3-propanediol were added to a three-necked flask, and 80 parts of ethanol were added as solvent. The mixture was reacted at 62°C for 5 h. The crude product was washed with deionized water to remove the solvent, and finally distilled under reduced pressure to obtain a yellow viscous liquid.

[0073] (2) Preparation of casting solution: 40 parts of hydroxyl-terminated polybutadiene and 10 parts of hexamethylene diisocyanate were mixed, and 1 part of catalyst (the catalyst was a mixed solution of dibutyltin dilaurate and tetrahydrofuran, the concentration of dibutyltin dilaurate in the catalyst was 0.5 wt%) and 120 parts of dimethylacetamide were added. The mixture was stirred thoroughly at 35°C for 3 h to form a prepolymer. 7 parts of the fluorinated chain extender prepared in step (1) were added, and the reaction was carried out for 4 h to obtain the polyurethane casting solution.

[0074] (3) Preparation of polyurethane membrane: The casting solution obtained in step (2) was allowed to stand for 2 hours to remove bubbles. The casting solution was then spread on a clean tetrafluoroethylene plate and allowed to stand at room temperature for 15 hours to remove the solvent. The solution was then dried in an oven at 100°C for 24 hours to obtain a fluorinated polyurethane gas separation membrane.

[0075] Example 7

[0076] The modified polyurethane gas separation membrane is prepared by the following steps:

[0077] (1) Preparation of fluorinated chain extender: 60 parts of hexafluorobutyl methacrylate and 8 parts of 2-amino-1,3-propanediol were added to a three-necked flask, and 80 parts of ethanol were added as solvent. The reaction was carried out at 65°C for 6 hours. The crude product was washed with deionized water to remove the solvent, and finally a yellow viscous liquid was obtained by vacuum distillation.

[0078] (2) Preparation of casting solution: 40 parts of poly(1,4-butanediol adipate) and 10 parts of toluene-2,4-diisocyanate were mixed, and 1 part of catalyst (the catalyst was a mixed solution of dibutyltin dilaurate and tetrahydrofuran, the concentration of dibutyltin dilaurate in the catalyst was 2 wt%) and 110 parts of dimethylformamide were added. The mixture was stirred thoroughly at 30°C for 5 h to form a prepolymer. 7 parts of the fluorinated chain extender prepared in step (1) were added, and the reaction was carried out for 4 h to obtain the polyurethane casting solution.

[0079] (3) Preparation of polyurethane membrane: The casting solution obtained in step (2) was allowed to stand for 2.5 hours to remove bubbles. The casting solution was then spread on a clean tetrafluoroethylene plate and allowed to stand at room temperature for 15 hours to remove the solvent. The solution was then dried in an oven at 40°C for 24 hours to obtain a fluorinated polyurethane gas separation membrane.

[0080] Comparative Example 1

[0081] The modified polyurethane gas separation membrane is prepared by the following steps:

[0082] (1) Preparation of casting solution: 40 parts of hydroxyl-terminated polybutadiene and 10 parts of isophorone diisocyanate were mixed, 1 part of 1 wt% dibutyltin dilaurate / tetrahydrofuran solution and 100 parts of tetrahydrofuran were added, and the mixture was stirred thoroughly at 40°C for 6 h to form a prepolymer. 7 parts of 1,4-butanediol were added, and the reaction was carried out for 4 h to obtain the polyurethane casting solution.

[0083] (2) Preparation of polyurethane membrane: The casting solution obtained in step (1) was allowed to stand for 3 hours to remove bubbles. The casting solution was then spread on a clean tetrafluoroethylene plate and allowed to stand at room temperature for 12 hours to remove the solvent. The membrane was then dried in an oven at 60°C for 24 hours to obtain a polyurethane gas separation membrane. The thickness of the membrane was measured to be 93 μm.

[0084] Comparative Example 2

[0085] The modified polyurethane gas separation membrane is prepared by the following steps:

[0086] (1) Preparation of unilateral fluorinated chain extender: 20 parts of dodecafluoroheptyl methacrylate and 5 parts of diethanolamine were added to a three-necked flask, and 50 parts of ethanol were added as solvent. The reaction was carried out at 60°C for 2 hours. The crude product was washed with deionized water to remove the solvent, and finally the unilateral fluorinated diol chain extender was obtained by vacuum distillation.

[0087] (2) Preparation of casting solution: 40 parts of hydroxyl-terminated polybutadiene and 10 parts of isophorone diisocyanate were mixed, and 1 part of 1 wt% dibutyltin dilaurate / tetrahydrofuran solution and 100 parts of tetrahydrofuran were added. The mixture was stirred thoroughly at 40°C for 6 h to form a prepolymer. 7 parts of the fluorinated chain extender prepared in step (1) were added, and the mixture was reacted for 4 h to obtain the polyurethane casting solution.

[0088] (3) Preparation of polyurethane membrane: The casting solution obtained in step (2) was allowed to stand for 3 hours to remove bubbles. The casting solution was then spread on a clean tetrafluoroethylene plate and allowed to stand at room temperature for 12 hours to remove the solvent. The membrane was then dried in an oven at 60°C for 24 hours to obtain a fluorinated polyurethane gas separation membrane. The thickness of the membrane was measured to be 104 μm.

[0089] Test example:

[0090] The polyurethane membranes prepared in Examples 1-5 and Comparative Examples 1-2 were placed in a gas permeation cell. Under conditions of 25°C and 0.1 MPa, the gas permeability P and ideal selectivity α were measured using pure CO2 and N2. i / j .

[0091] The formula for calculating gas permeability P is as follows:

[0092]

[0093] In the formula: P is the gas permeability coefficient (barrer [1 barrer = 1 × 10⁻⁶)). -10 cm 3 (STP) ×cm / (cm 2 ×s×cmHg)]); Q is the cumulative amount of gas permeation from the start of permeation to time t (cm). 3 A is the area of ​​the membrane (cm²). 2 ); l is the film thickness (cm); ΔP is the pressure difference between the upstream and downstream sides (MPa).

[0094] Separation selectivity α i / j The calculation formula is shown below:

[0095]

[0096] In the formula: α i / j This indicates the ideal selectivity of the membrane for the gaseous components CO2 and N2; P iP represents the permeability coefficient (barrer) of CO2. j This represents the permeability coefficient (barrer) of the gaseous component N2.

[0097] The test results are shown in the table below.

[0098] Table 1 Comparison of Gas Separation Effects

[0099]

[0100]

[0101] As shown in Table 1, the polyurethane membrane prepared with the addition of double-sided fluorinated diol chain extenders has a much higher CO2 permeability and CO2 / N2 selectivity than the polyurethane membrane without fluorine, and also has better gas separation performance than the polyurethane membrane prepared with single-sided fluorinated chain extenders.

[0102] Figure 2 This is the infrared spectrum of the fluorinated chain extender of Example 1 of the present invention. Figure 2 It can be seen that fluorinated chain extenders are present at 3340 cm⁻¹ -1 The absorption peak at 1690 cm⁻¹ belongs to the stretching vibration of OH. -1 and 1264cm -1 The absorption peak at 1172 cm⁻¹ belongs to the stretching vibrations of C=O and CO. -1 The absorption peak at this point belongs to the stretching vibration of CF, indicating that the fluorinated chain extender has been successfully synthesized.

[0103] Figure 3 This is the infrared spectrum of the modified polyurethane film of Example 1 of the present invention. Figure 3 It can be seen that fluorinated polyurethane at 3306 cm⁻¹ -1 and 1521cm -1 The absorption peak at 1650 cm⁻¹ belongs to the stretching and bending vibrations of the NH group in the carbamate bond. -1 and 1247cm -1 The absorption peak at 1417 cm⁻¹ belongs to the stretching vibrations of C=O and CO. -1 This is a CN bending vibration, 10¹³ cm. -1 The absorption peak at 1237 cm⁻¹ is due to the asymmetric stretching vibration of COC in the urethane group. -1 The absorption peak at 2254 cm⁻¹ corresponds to the stretching vibration of CF, indicating the formation of urethane groups and the successful incorporation of fluorinated chain extenders into the polyurethane molecule. -1 The absence of an NCO absorption peak indicates that the NCO groups have completely reacted.

[0104] Figure 4 This is a surface SEM image of the modified polyurethane film of Example 1 of the present invention. Figure 4 It can be seen that the membrane surface is uniform and dense, indicating that the synthesized membrane is a defect-free and dense membrane.

[0105] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A modified polyurethane gas separation membrane, characterized in that, The modified polyurethane gas separation membrane comprises polyurethane soft segments and fluorinated hard segments; the polyurethane soft segments are composed of oligomeric diols, and the fluorinated hard segments are composed of fluorinated chain extenders and isocyanates; the fluorinated chain extender refers to a fluorinated chain extender having two fluorinated alkyl side chains. The modified polyurethane gas separation membrane comprises the following components by weight: 3-7 parts of fluorinated chain extender; 20-40 parts of oligomeric diol; 5-10 parts of diisocyanate; 1-2 parts of catalyst; and 100-120 parts of solvent. By weight percentage, the fluorinated chain extender comprises the following components: 40-60 parts of fluorinated methacrylate; 5-8 parts of 2-amino-1,3-propanediol; and 60-80 parts of ethanol. The fluorinated methacrylate is trifluoroethyl methacrylate, pentafluoropropyl methacrylate, hexafluorobutyl methacrylate, nonafluorohexyl methacrylate, dodecafluoroheptyl methacrylate, or heptadecafluorodecyl methacrylate.

2. The modified polyurethane gas separation membrane according to claim 1, characterized in that, The fluorinated chain extender is obtained by reacting fluorinated methacrylate with 2-amino-1,3-propanediol, washing with water, and then distilling under reduced pressure.

3. The modified polyurethane gas separation membrane according to claim 1, characterized in that, The oligomeric diol is one or more of hydroxyl-terminated polybutadiene, polytetramethylene glycol, polycaprolactone diol, polypropylene glycol, and poly(1,4-butanediol adipate); the diisocyanate is isophorone diisocyanate, hexamethylene diisocyanate, 4,4'-diisocyanate diphenylmethane, toluene-2,4-diisocyanate, or 1,5-naphthalene diisocyanate; and the solvent is one of tetrahydrofuran, acetone, butanone, ethyl acetate, dimethylformamide, and dimethylacetamide.

4. The modified polyurethane gas separation membrane according to claim 1, characterized in that, The catalyst is a mixed solution of dibutyltin dilaurate and tetrahydrofuran, and the concentration of dibutyltin dilaurate in the catalyst is 0.5~2 wt%.

5. The modified polyurethane gas separation membrane according to claim 1, characterized in that, The concentration of dibutyltin dilaurate in the catalyst is 1.0 wt%.

6. The modified polyurethane gas separation membrane according to claim 1, characterized in that, The thickness of the modified polyurethane gas separation membrane is 30~200 μm.

7. A method for preparing the modified polyurethane gas separation membrane according to any one of claims 1-6, characterized in that, The preparation method includes the following steps, in parts by mass: S1: Preparation of fluorinated chain extender: Add ethanol to fluorinated methacrylate and 2-amino-1,3-propanediol, mix and react to obtain crude product, wash with water and distill under reduced pressure to obtain fluorinated chain extender solution; S2: Preparation of casting solution: Mix oligomeric diol with diisocyanate, add catalyst and solvent, stir to obtain prepolymer, then add fluorinated chain extender prepared in step S1, after chain extension reaction, polyurethane casting solution is obtained. S3: After the casting solution obtained in S2 is allowed to stand to remove bubbles, it is spread evenly on a tetrafluoroethylene plate, allowed to stand again for 10~15h to remove solvent, and then dried to obtain a modified polyurethane gas separation membrane. In step S1, the temperature of the mixing reaction is 60~65℃ and the time is 4~6h; In step S2, the stirring temperature is 30~40℃ and the time is 3~6h; the chain extension reaction time is 1~4h. In step S3, the time for static degassing is 2-3 hours; the drying temperature is 40-100℃ and the time is 24 hours.

8. The application of the modified polyurethane gas separation membrane according to any one of claims 1-6, characterized in that, The modified polyurethane separation membrane is used to capture CO2 from flue gas.

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