Polypropylene / covalent organic framework hybrid hollow fiber oxygenation membrane with gradient structure and method of making the same

Abstract

The present application relates to polypropylene / covalent organic framework hybrid hollow fiber oxygenation membrane with gradient structure and its preparation method; the covalent organic framework material is ultrasonically dispersed for 5-20min, and then cell crushing is carried out for 5-20min to be dispersed in a diluent to obtain a dispersion liquid; polypropylene is added to the dispersion liquid, and after heating and stirring, standing is carried out to obtain a casting solution, and the casting solution is used as raw material to spin by using a thermally induced phase separation method to obtain a hybrid hollow fiber oxygenation membrane. The oxygenation membrane is a loose porous gradient structure gradually increasing from the dense skin layer on the surface to the main body, and the covalent organic framework is gradiently distributed in the membrane. The hybrid hollow fiber oxygenation membrane has excellent oxygen and carbon dioxide gas permeability and plasma leakage resistance, the carbon dioxide transmission capacity is 65.3ml / (min·cm 2 ·bar), the oxygen transmission capacity is 53.5ml / (min·cm 2 ·bar), and the plasma leakage resistance time is 124h.

Description

Technical Field

[0001] This application belongs to the field of membrane technology, specifically relating to a hybrid hollow fiber oxygenation membrane with a gradient structure based on a covalent organic framework and its preparation method. Background Technology

[0002] Extracorporeal membrane oxygenation (ECMO) devices are primarily used to provide continuous extracorporeal respiration and circulation for patients with severe cardiopulmonary failure, also known as artificial lungs. Ideal ECMO membrane materials should possess high permeability and good resistance to plasma leakage. Polypropylene (PP) is one of the commercially available oxygenation membrane materials due to its advantages such as low cost, high gas permeability, good biocompatibility, and high surface hydrophobicity. However, most PP membranes prepared using existing technologies have a homogeneous structure. Their high porosity and large pore size make them easily wetted by liquids, increasing the risk of plasma leakage and resulting in an oxygenation membrane lifespan of less than 6 hours. Therefore, unlike the homogeneous porous structures of existing technologies, developing PP membranes with a gradient structure consisting of a dense skin layer and a porous support layer is of great significance in preventing plasma leakage while maintaining high gas permeability.

[0003] Currently, covalent organic framework materials are developing rapidly, possessing characteristics such as large specific surface area, high-density functional groups, and high mechanical properties. They exhibit water stability, high thermal stability, solvent stability, and high mechanical properties, along with interconnected, uniform, interconnected, and stable ordered mass transfer channels, making them widely used in separation systems. Their porous channels facilitate the permeation of oxygen and carbon dioxide, and polar groups can interact with polar carbon dioxide. Hybridizing two-dimensional covalent organic framework materials with polypropylene allows for a gradient distribution of the covalent organic framework material, increasing the polymer concentration on the membrane surface. Simultaneously, it provides additional channels for the rapid transport of oxygen and carbon dioxide, and the intertwining of the molecular chains enhances the mechanical properties of the oxygenation membrane, achieving the goal of improving the clinical performance of hybrid hollow fiber oxygenation membranes.

[0004] Therefore, in response to the contradictory problems of gas permeability and blood plasma leakage resistance in currently commercially available oxygenation membranes, this invention prepares a hybrid membrane by physically blending a covalent organic framework with polypropylene and then using a thermally induced phase separation (TIPS) method. This is expected to solve these problems and promote the development of the oxygenation membrane field. Summary of the Invention

[0005] The purpose of this application is to provide a hybrid hollow fiber oxygenation membrane with a gradient structure based on a covalent organic framework and its preparation method, so as to solve the problem that the surface of polypropylene oxygenation membranes in the prior art has micropores, which easily leads to plasma leakage during the oxygenation process.

[0006] To achieve the above objectives, one technical solution adopted in this application is:

[0007] A polypropylene / covalent organic framework hybrid hollow fiber oxygenation membrane with a gradient structure; the hybrid hollow fiber oxygenation membrane is a hollow fiber oxygenation membrane based on the hybridization of covalent organic framework and polypropylene material. The oxygenation membrane has a gradient structure that gradually increases in size from a dense skin layer on the surface to a loose and porous body, with the covalent organic framework exhibiting a gradient distribution within the membrane. The content gradually decreases from the surface to the body. A schematic diagram of the membrane structure is shown below. Figure 1 As shown.

[0008] The present invention discloses a method for preparing a polypropylene / covalent organic framework hybrid hollow fiber oxygen membrane with a gradient structure. The method involves first ultrasonically dispersing the covalent organic framework material for 5-20 minutes, then uniformly dispersing it in a diluent after cell disruption for 5-20 minutes to obtain a dispersion. Polypropylene is then added to the dispersion, heated and stirred, and allowed to stand to obtain a casting solution. The casting solution is used as a raw material for spinning using a thermally induced phase separation method to obtain the hybrid hollow fiber oxygen membrane.

[0009] The mass ratio of the covalent organic framework material to polypropylene is (0.3-1.5):100.

[0010] The diluent includes one or more combinations of dibutyl phthalate, dioctyl phthalate, trioctyl acetyl citrate, tributyl citrate, and trioctyl citrate; the mass ratio of the covalent organic framework material to the diluent is (0.3-1.5):150.

[0011] The conditions for heating, stirring, and then allowing the mixture to stand are as follows: heat to 180-210℃ and stir for 6-12 hours, then stop stirring, raise the temperature to 190-220℃, and allow the mixture to stand for 6-12 hours to remove bubbles before obtaining the casting solution.

[0012] The thermally induced phase separation spinning method is as follows: the casting solution is kept at a constant temperature of 220-240℃, and the casting solution is extruded through a spinneret and introduced into a water coagulation bath at room temperature for solidification and molding. The spinning speed is 40000-70000 mm / min, and the core liquid flow rate is 1.8-3 ml / min.

[0013] In the preparation method of the present invention, the hybrid hollow fiber oxygen membrane is fully immersed in an extraction solution to extract and remove the diluent, and then dried; the extraction solution includes one or more of anhydrous ethanol, isopropanol, n-heptane, and n-hexane.

[0014] The present invention relates to the application of a polypropylene / covalent organic framework hybrid hollow fiber oxygenation membrane with a gradient structure as an oxygenation membrane in extracorporeal membrane lung oxygenation.

[0015] The advantages of this application, which differ from existing technologies, are:

[0016] 1. The hybrid hollow fiber oxygen membrane of this application uses a hybrid dispersed covalent organic framework material, which possesses characteristics such as large specific surface area, high-density functional groups, and high mechanical properties. In this hybrid hollow fiber oxygen membrane, the covalent organic framework material exhibits a gradient distribution, altering the membrane pore structure and resulting in a gradient structure—dense on the surface and porous internally—unlike existing technologies, effectively preventing plasma leakage. The embedding of the covalent organic framework provides additional adsorption and transport channels for oxygen and carbon dioxide; the entanglement of the covalent organic framework with polypropylene molecular chains improves the mechanical properties of the hybrid hollow fiber oxygen membrane, while avoiding the reduction in gas transport performance caused by efforts to extend membrane lifespan in current polypropylene oxygen membrane production. The hybrid hollow fiber oxygen membrane of this application exhibits excellent oxygen and carbon dioxide gas permeability and anti-plasma leakage properties, with a carbon dioxide transport capacity of 65.3 ml / (min·cm). 2 The carbon dioxide transport capacity of the existing unhybridized polypropylene membrane is 7.12 ml / (min·cm). 2 It is 9 times faster than that of other oxygen carriers (bar); its oxygen transport capacity is 53.5 ml / (min·cm). 2 The oxygen transport capacity of the existing unhybridized polypropylene membrane is 8.33 ml / (min·cm). 2 It has 6 times the resistance to plasma leakage (bar) and a plasma leakage resistance time of 124 hours, which is approximately 21 times that of existing unhybridized polypropylene membranes (6 hours). [1] .

[0017] 2. The preparation method of this application, by dispersing covalent organic framework materials in casting solution and spinning them by thermally induced phase separation, produces hybrid hollow fiber oxygenation membranes that are highly competitive among oxygenation membranes used in extracorporeal membrane lung oxygenation.

[0018] [1]J.Li,T.He,H.Chen,Y.Cheng,E.Drioli,Z.Wang,Z.Cui,Preparation ofHyflon AD / Polypropylene Blend Membrane for Artificial Lung,Membranes 13(2023)665.https: / / doi.org / 10.3390 / membranes13070665. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the cross-sectional structure of a polypropylene / covalent organic framework hybrid hollow fiber oxygen membrane with a gradient structure.

[0020] Figure 2 This is a morphology diagram of the prepared polypropylene / covalent organic framework hybrid hollow fiber oxygen membrane with a gradient structure.

[0021] Figure 3 This is a comparison chart of the oxygen and carbon dioxide permeation rate performance of the membranes prepared by the methods in Examples 1-4 and the polypropylene membranes of the prior art. Detailed Implementation

[0022] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments:

[0023] Weigh the materials according to the formula. The mass percentage of the covalent organic framework in the material formula is 0.3-1.5% of the mass of polypropylene, and the mass ratio of the covalent organic framework to the diluent is (0.3-1.5):150. First, add a portion of the materials, then add the covalent organic framework material to the diluent. After ultrasonic dispersion and cell disruption, the covalent organic framework material is evenly dispersed by ultrasonication. Then add the polypropylene, heat to 180-210℃ and stir for 6-12 hours to fully dissolve the polypropylene and avoid large crystals and agglomeration. Stop stirring and raise the temperature to 190-220℃. Let it stand for 6-12 hours to degas and obtain the casting solution.

[0024] Using casting solution as raw material, spinning is performed using a twin-screw spinning machine. The casting solution is extruded and introduced into a water coagulation bath at room temperature. The twin-screw is kept at a constant temperature of 165-175℃, the spinneret is kept at a constant temperature of 155-165℃, the outer diameter and inner diameter of the annular spinneret are 1.2 mm and 0.7 mm, respectively, the distance between the spinneret and the surface of the water coagulation bath is 2 cm, the spinning speed is 40,000-70,000 mm / min, and the core liquid flow rate is 1.8-3 ml / min.

[0025] The formed hollow fiber membrane is added to the solvent, and the solvent is replaced every 8-12 hours. The extraction is carried out by solvent exchange for 2-3 days.

[0026] The hollow fiber membrane obtained after extraction is placed in a room temperature oven and dried for 1-2 days.

[0027] Example 1:

[0028] A hybrid hollow fiber oxygenation membrane is prepared using the following steps:

[0029] Weigh 18g of dioctyl phthalate, 6mg of covalent organic framework COF-316, and 2g of polypropylene. Add the weighed dioctyl phthalate and COF-316 to a 50ml three-necked flask and sonicate for 5 minutes until the COF-316 is evenly dispersed, resulting in a light gray suspension. After cell disruption and sonication for 5 minutes, add 2g of polypropylene to the suspension. Place the suspension in the reactor of a hollow fiber membrane spinning machine and stir at 180℃ for 6 hours. Heat the stirred casting solution to 190℃ and let it stand for 6 hours, ready for use in preparing hollow fiber membranes.

[0030] Using casting solution as raw material, hollow fiber membrane spinning was performed using a hollow fiber membrane spinning machine. The casting solution was extruded and introduced into a water coagulation bath at room temperature. The twin-screw extruder was kept at a constant temperature of 165℃, and the spinneret was kept at a constant temperature of 155℃. The outer diameter and inner diameter of the annular spinneret were 1.2 mm and 0.7 mm, respectively. The distance between the spinneret and the surface of the water coagulation bath was 2 cm. The spinning speed was 40,000 mm / min, and the core liquid flow rate was 1.8 ml / min.

[0031] The formed hollow fiber membrane was extracted in anhydrous ethanol for 2 days to ensure the removal of diluent, and the anhydrous ethanol was replaced twice during the process. Then it was dried in an oven for 1 day.

[0032] Example 2:

[0033] A hybrid hollow fiber oxygenation membrane is prepared using the following steps:

[0034] Weigh out 8g of dioctyl phthalate, 10mg of covalent organic framework COF-300, and 2g of polypropylene. Add the weighed dioctyl phthalate and COF-300 to a 50ml three-necked flask, and sonicate for 10min until the COF-300 is evenly dispersed, yielding a light gray suspension. After cell disruption and sonication for 10min, add 2g of polypropylene to the suspension. Place the suspension in the reactor of a hollow fiber membrane spinning machine and stir at 190℃ for 8h. Heat the stirred casting solution to 200℃ and let it stand for 8h, ready for use in preparing hollow fiber membranes.

[0035] Using casting solution as raw material, hollow fiber membrane spinning was performed using a hollow fiber membrane spinning machine. The casting solution was extruded and introduced into a water coagulation bath at room temperature. The twin-screw extruder was kept at a constant temperature of 170℃, and the spinneret was kept at a constant temperature of 160℃. The outer diameter and inner diameter of the annular spinneret were 1.2 mm and 0.7 mm, respectively. The distance between the spinneret and the surface of the water coagulation bath was 2 cm. The spinning speed was 50,000 mm / min, and the core liquid flow rate was 2.2 ml / min.

[0036] The formed hollow fiber membrane was extracted in anhydrous ethanol for 2 days to ensure the removal of diluent, and the anhydrous ethanol was replaced twice during the process. Then it was dried in an oven for 1 day.

[0037] Example 3:

[0038] A hybrid hollow fiber oxygenation membrane is prepared using the following steps:

[0039] Weigh 4.6667 g of dioctyl phthalate, 20 mg of covalent organic framework (COF-LZU1), and 2 g of polypropylene. Add the weighed dioctyl phthalate and COF-LZU1 to a 50 mL three-necked flask, and sonicate for 15 min until the COF-LZU1 is evenly dispersed, resulting in a light gray suspension. After cell disruption and sonication for 15 min, add 2 g of polypropylene to the suspension. Place the suspension in the reactor of a hollow fiber membrane spinning machine and stir at 200 °C for 10 h. Heat the stirred casting solution to 210 °C and let it stand for 10 h, ready for use in preparing hollow fiber membranes.

[0040] Using casting solution as raw material, hollow fiber membrane spinning was performed using a hollow fiber membrane spinning machine. The casting solution was extruded and introduced into a water coagulation bath at room temperature. The twin-screw extruder was kept at a constant temperature of 175℃, and the spinneret was kept at a constant temperature of 165℃. The outer diameter and inner diameter of the annular spinneret were 1.2 mm and 0.7 mm, respectively. The distance between the spinneret and the surface of the water coagulation bath was 2 cm. The spinning speed was 60,000 mm / min, and the core liquid flow rate was 2.6 ml / min.

[0041] The formed hollow fiber membrane was extracted in anhydrous ethanol for 3 days to ensure the removal of diluent, and the anhydrous ethanol was replaced twice during the process. Then it was dried in an oven for 2 days.

[0042] Example 4:

[0043] A hybrid hollow fiber oxygenation membrane is prepared using the following steps:

[0044] Weigh out 3g of dioctyl phthalate, 40mg of covalent organic framework JUC-521, and 2g of polypropylene. Add the weighed dioctyl phthalate and covalent organic framework JUC-521 to a 50mL three-necked flask, and sonicate for 20min until the covalent organic framework JUC-521 is evenly dispersed, resulting in a light gray suspension. After cell disruption and sonication for another 20min, add 2g of polypropylene to the suspension. Place the suspension in the reactor of a hollow fiber membrane spinning machine and stir at 210℃ for 12h. The stirred casting solution is then heated to 220℃ and allowed to stand for 12h, ready for use in the preparation of hollow fiber membranes.

[0045] Using casting solution as raw material, hollow fiber membrane spinning was performed using a hollow fiber membrane spinning machine. The casting solution was extruded and introduced into a water coagulation bath at room temperature. The twin-screw extruder was kept at a constant temperature of 180℃, and the spinneret was kept at a constant temperature of 170℃. The outer diameter and inner diameter of the annular spinneret were 1.2 mm and 0.7 mm, respectively. The distance between the spinneret and the surface of the water coagulation bath was 2 cm. The spinning speed was 70,000 mm / min, and the core liquid flow rate was 3 ml / min.

[0046] The formed hollow fiber membrane was extracted in anhydrous ethanol for 3 days to ensure the removal of diluent, and the anhydrous ethanol was replaced twice during the process. Then it was dried in an oven for 2 days.

[0047] The hybrid hollow fiber oxygenation membrane prepared in Example 1 was characterized by scanning electron microscopy and analyzed to obtain... Figure 2 . Figure 2 This is a scanning electron microscope image of the hybrid hollow fiber oxygen membrane of Embodiment 1 of this application.

[0048] like Figure 2 As shown, the hybrid hollow fiber oxygenated membrane prepared in Example 1 has a gradient structure that gradually increases in size from a dense skin layer on the surface to a loose and porous body.

[0049] The hybrid hollow fiber oxygen membrane has a thickness of about 500 μm, the cross-section of the support layer has a loose porous structure, and the surface is dense.

[0050] Experimental Example 1: Test of oxygen and carbon dioxide transport performance of hybrid hollow fiber membranes

[0051] The hybrid hollow fiber oxygenation membranes prepared in Examples 1 to 4 and the hollow fiber membranes prepared in the comparative examples were encapsulated into membrane modules with epoxy resin AB glue. Oxygen or carbon dioxide at 1 bar was introduced into the membrane modules, and the gas flow rate was measured with a soap membrane flow meter. The oxygen permeation rate and carbon dioxide permeation rate of each fiber membrane were calculated, and the data in the table below were obtained.

[0052] Table 1 Gas permeation performance of membranes modified under different covalent organic framework conditions

[0053]

[0054] like Figure 3 To test the carbon dioxide and oxygen permeation rates under pressure, the hybrid membrane with added covalent organic frameworks exhibited significantly better carbon dioxide and oxygen transport rates than the polypropylene membrane without covalent organic frameworks. This is mainly because the covalent organic frameworks, with their high content of imine and benzene ring groups, high-density pores, and large specific surface area, enhance the dissolution-diffusion process of oxygen and carbon dioxide molecules through the membrane. Furthermore, the good interaction and compatibility between the covalent organic framework nanoparticles and polypropylene enhance the membrane's free volume, reducing the resistance to gas transport within the membrane. These multiple mechanisms work together to give the prepared hybrid membrane highly efficient gas transport performance. In summary, the hybrid membrane in Example 2 exhibits the best oxygen and carbon dioxide gas permeability, with a carbon dioxide transport capacity of 65.3 ml / (min·cm). 2 The carbon dioxide transport capacity of the existing unhybridized polypropylene membrane is 7.12 ml / (min·cm). 2 It is 9 times faster than that of other oxygen carriers (bar); its oxygen transport capacity is 53.5 ml / (min·cm).2 The oxygen transport capacity of the existing unhybridized polypropylene membrane is 8.33 ml / (min·cm). 2 It is 6 times stronger than ·bar) and has a plasma leakage resistance time of 124h, which is about 21 times that of the existing unhybridized polypropylene membrane in 6h.

[0055] Although the present invention has been described above in conjunction with the accompanying drawings, the present invention 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 modifications under the guidance of the present invention without departing from the spirit of the present invention, and these modifications are all within the protection scope of the present invention.

Claims

1. A polypropylene / covalent organic framework hybrid hollow fiber oxygenation membrane with a gradient structure, characterized in that, The hybrid hollow fiber oxygen membrane is a hollow fiber oxygen membrane based on a hybrid of covalent organic framework and polypropylene material. The oxygen membrane has a gradient structure from a dense outer layer to a loose and porous core, with the covalent organic framework exhibiting a gradient distribution within the membrane. The covalent organic framework material is first ultrasonically dispersed for 5-20 min, then cell-broken for 5-20 min and uniformly dispersed in a diluent to obtain a dispersion. Polypropylene is added to the dispersion, heated and stirred, and then allowed to stand to obtain a casting solution. The casting solution is used as raw material and spun using a thermally induced phase separation method to obtain the hybrid hollow fiber oxygen membrane. The mass ratio of covalent organic framework material to diluent is (0.3~1.5):150, and the mass ratio of covalent organic framework material to polypropylene is (0.3~1.5):

100. The thermally induced phase separation spinning method involves maintaining the casting solution at a constant temperature of 220-240℃, extruding the casting solution through a spinneret and introducing it into a water coagulation bath at room temperature for solidification, with a spinning speed of 40,000~70,000. The core fluid flow rate is 1.8~3 ml / min.

2. A method for preparing a polypropylene / covalent organic framework hybrid hollow fiber oxygen membrane with a gradient structure as described in claim 1, characterized in that, The covalent organic framework material is first ultrasonically dispersed for 5-20 min, then cell-broken for 5-20 min and uniformly dispersed in a diluent to obtain a dispersion. Polypropylene is added to the dispersion, heated and stirred, and then allowed to stand to obtain a casting solution. The casting solution is used as a raw material and spun using a thermally induced phase separation method to obtain a hybrid hollow fiber oxygen membrane.

3. The preparation method according to claim 2, characterized in that: The diluent includes one or more combinations of dibutyl phthalate, dioctyl phthalate, trioctyl acetyl citrate, tributyl citrate, and trioctyl citrate.

4. The preparation method according to claim 2, characterized in that: The conditions for heating and stirring followed by standing are as follows: heat to 180-210℃ and stir for 6-12 h, then stop stirring, raise the temperature to 190-220℃ and let stand for 6-12 h to remove bubbles, and then obtain the casting solution.

5. The preparation method according to claim 2, characterized in that: The solidified hollow fiber oxygen membrane is thoroughly immersed in the extraction solution to extract and remove the diluent, and then dried.

6. The preparation method according to claim 5, characterized in that: The extract includes one or more of anhydrous ethanol, isopropanol, n-heptane, and n-hexane.

7. The application of a polypropylene / covalent organic framework hybrid hollow fiber oxygenation membrane with a gradient structure as described in claim 1 as an oxygenation membrane in extracorporeal membrane lung oxygenation.

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