Polyether ether ketone hollow fiber loose nanofiltration membrane, preparation method and application thereof
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- JILIN UNIVERSITY
- Filing Date
- 2026-03-04
- Publication Date
- 2026-06-02
Smart Images
Figure CN121775660B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of nanofiltration membrane technology, specifically relating to a polyether ether ketone (PEEK) hollow fiber loose nanofiltration membrane and its preparation method and application, especially the application of high-strength, high-flux PEEK hollow fiber loose membrane prepared by post-stretching technology in the separation of dyes and salts. Background Technology
[0002] Nanofiltration membrane technology, as a highly efficient and energy-saving separation process, has core application value in many application scenarios, especially in the separation of dye and inorganic salt mixtures. This process requires the separation membrane to maintain near-complete retention of large dye molecules (such as Congo red and methylene blue, with molecular weights typically >600 Da) while allowing efficient permeation of small inorganic salt molecules (such as NaCl and Na₂SO₄) to achieve dye desalination or concentration. Furthermore, the treatment system often exhibits extreme conditions such as strong acidity, strong alkalinity, high salinity, or the presence of organic solvents, requiring the membrane material itself to possess excellent chemical stability and long-term operational durability.
[0003] Polyetheretherketone (PEEK), a semi-crystalline engineering plastic, is considered an ideal candidate material due to its excellent high-temperature resistance, outstanding mechanical strength, and unparalleled chemical corrosion resistance. However, PEEK's highly rigid and orderly aromatic molecular chain structure, along with its strong tendency to crystallize, is not only the source of all its superior properties but also the fundamental obstacle to processing it into a separation membrane with a nanoscale interconnected porous structure. This processing challenge has directly led to a fundamental compromise in existing technological approaches: to obtain a porous structure, the effective content of PEEK must be significantly reduced, thereby sacrificing its core mechanical properties. This results in a "porosity equals weakness" dilemma, failing to realize the material's inherent strength potential.
[0004] Specifically, existing technologies have mainly formed two preparation routes with inherent defects: First, non-solvent-induced phase separation (NIPS), which relies on strong acid solvents and has extremely low polymer concentrations (usually below 20%), resulting in severely insufficient mechanical strength of the membrane; Second, thermally induced phase separation (TIPS) and its blending derivative route, although avoiding strong acids, still require low PEEK content formulations (below 50%) to form pores and rely on extraction to create pores. The resulting membranes still have low mechanical strength, and the formed pores are mostly isotropic and have a wide pore size distribution, making it difficult to precisely control the separation selectivity.
[0005] Therefore, there is an urgent need in this field to develop an innovative method for preparing porous PEEK nanofiltration membranes. This method must overcome the limitations of existing approaches and ensure the intrinsic high strength and corrosion resistance of PEEK without sacrificing the separation performance of the PEEK hollow fibers, thereby simultaneously improving the membrane's separation performance and mechanical strength. Summary of the Invention
[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a polyetheretherketone hollow fiber loose nanofiltration membrane with high dye rejection rate, high salt permeability, high throughput and excellent mechanical and chemical stability, as well as its preparation method and application in dye and salt separation.
[0007] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows.
[0008] In a first aspect, the present invention provides a method for preparing a porous nanofiltration membrane made of polyetheretherketone resin hollow fibers, comprising the following steps:
[0009] S1. Blending and Granulation:
[0010] 60wt%~90wt% of dried polyether ether ketone powder and 10wt%~40wt% of dried polyether imide resin (PEI) powder are blended, and the resulting mixture is melt-extruded and granulated to obtain blended resin particles.
[0011] S2. Extrusion and cooling of precursor fibers:
[0012] The blended resin particles are fed into a hollow fiber extruder for melt extrusion, cooled and solidified, and then drawn and wound to obtain the blended precursor hollow fiber.
[0013] S3. Heat treatment (annealing):
[0014] The hollow fiber of the blend precursor was heat-treated at 220~300℃ for 1~5h to obtain annealed hollow fiber;
[0015] S4. Selective extraction for pore formation:
[0016] The annealed hollow fibers were immersed in a selective extractant and extracted for 2-48 hours. The extracted hollow fibers were then washed repeatedly by immersing them in isopropanol and deionized water, and then stored in a 10-70 wt% glycerol aqueous solution for 24-48 hours to obtain nascent polyetheretherketone hollow fibers.
[0017] The selective extractant is a mixed solution of ethanolamine and N-methylpyrrolidone (NMP), with the volume fraction of ethanolamine being 10%~30% and the volume fraction of NMP being 70%~90%.
[0018] S5. Post-stretching treatment:
[0019] First, the nascent polyetheretherketone hollow fibers are hot-stretched at 100~250℃ with a hot stretching ratio of 100~300%, then heat-set for 10~30 minutes, and then wound up to obtain a loose polyetheretherketone hollow fiber nanofiltration membrane.
[0020] Alternatively, the nascent polyetheretherketone hollow fibers are first cold-stretched at 20-25°C with a cold stretching ratio greater than 0% and less than or equal to 15%, and then cold-set for 1-5 minutes. Subsequently, they are hot-stretched at 100-250°C with a hot stretching ratio of 100-300%, and then hot-set for 10-30 minutes. The fibers are then wound up to obtain a loose polyetheretherketone hollow fiber nanofiltration membrane.
[0021] Preferably, in step S1, the polyetheretherketone powder and the polyetherimide powder have the same mesh size; more preferably, the particle size of both the polyetheretherketone powder and the polyetherimide powder is ≤48μm.
[0022] Preferably, in step S1, the drying temperature is independently 120~160℃.
[0023] Preferably, in step S1, the drying time is 8~12h independently.
[0024] Preferably, in step S1, the polyetheretherketone powder and polyetherimide powder are co-mixed in a powder mixer for 3 to 5 times, with each mixing time being 15 to 30 seconds.
[0025] Preferably, in step S1, the temperature of the melt extrusion is 350~400℃; more preferably, the temperature of the melt extrusion is 360~375℃.
[0026] Preferably, in step S1, the length of the blended resin particles is 2.5~3.5mm.
[0027] Preferably, in step S1, after granulation, the granules are washed 3-5 times with deionized water and ethanol respectively, and then vacuum dried to obtain blended resin particles.
[0028] Preferably, in step S2, the outer diameter of the die head of the hollow fiber extruder is 4~6.4mm and the inner diameter is 3.4~5.6mm.
[0029] Preferably, in step S2, the temperatures of the first, second, and third zones and the die head zone of the hollow fiber extruder are 250~310℃, 340~360℃, 350~370℃ and 345~365℃, respectively.
[0030] Preferably, in step S2, the motor frequencies of the main motor speed and the feeding speed of the hollow fiber extruder are 10~30Hz and 8~24Hz, respectively.
[0031] Preferably, in step S2, air cooling is used for curing, and the air cooling temperature is 20~25℃.
[0032] Preferably, in step S2, the traction winding speed is 4.5~15m / min.
[0033] Preferably, in step S2, the outer diameter of the hollow fiber in the blended precursor is 0.6~1.2mm and the inner diameter is 0.4~0.9mm.
[0034] Preferably, in step S3, the hollow fibers of the blend precursor are heat-treated at 260~300℃ for 1~3 hours.
[0035] Preferably, in step S5, the cold stretching rate is 3~5 mm / min, and the hot stretching rate is 5~20 mm / min respectively.
[0036] Secondly, the present invention also provides a polyetheretherketone resin hollow fiber loose nanofiltration membrane prepared by the above-mentioned method for preparing polyetheretherketone resin hollow fiber loose nanofiltration membrane.
[0037] Preferably, the porosity of the polyetheretherketone resin hollow fiber loose nanofiltration membrane is 20-80%, and the average pore size is 0.01-0.03 μm.
[0038] Thirdly, the present invention also provides the application of the above-mentioned polyetheretherketone resin hollow fiber loose nanofiltration membrane in the separation of dyes and salts.
[0039] The principle of this invention is as follows: The reason why PEEK has long been unable to overcome the "weakness due to pores" dilemma lies in the fact that the general understanding of the "stretching" or "drawing" mechanism in this field is mainly based on the successful experience with polyolefin materials such as polypropylene (PP). The core principle of this experience is that a rigid elastic material is extruded and crystallized under a high stress field to form a lamellar structure with parallel arrangement perpendicular to the base direction. Micropores are "created" by stretching and destroying the lamellar structure. However, for high-performance engineering plastics like PEEK, its inherent high glass transition temperature and chain rigidity make it extremely prone to brittle fracture under the classic "stretching-induced pores" conditions based on polyolefins, making it difficult to achieve effective pore formation. This objective difference has led to a general lack of motivation among those skilled in the art to apply the "post-stretching" process to PEEK porous membranes to achieve structural optimization. As a result, related research has long been limited to improving the initial pore-forming process itself, resulting in the lack of exploration of the technical path of "first constructing a high-strength matrix, and then precisely optimizing the pores".
[0040] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0041] The polyetheretherketone hollow fiber loose nanofiltration membrane of the present invention has high strength (tensile strength ≥80Mpa), high flux (pure water flux of 10~25L / (m²·h·bar)) and excellent resistance to acid, alkali and organic solvent corrosion. It has a rejection rate of more than 95% for dye molecules with high molecular weight (≥600Da) and a rejection rate of less than 10% for monovalent salts such as sodium chloride.
[0042] The polyetheretherketone hollow fiber loose nanofiltration membrane of the present invention is suitable for efficient separation processes in harsh environments such as dye desalination, dyeing and printing wastewater treatment, and high-value-added dye recovery. Attached Figure Description
[0043] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0044] Figure 1 This is a schematic diagram of the fiber drawing machine used in a specific embodiment of the present invention;
[0045] Among them, 1. raw yarn roller, 2. guide clamp, 3. hot stretching roller, 4. first heating channel, 5. first hot stretching roller group, 6. second heating channel, 7. second hot stretching roller group, 8. winding device, 9. first hot air box, 10. second hot air box.
[0046] Figure 2 This is a cross-sectional view of the PEEK hollow fiber loose nanofiltration membrane prepared in Example 1 of the present invention.
[0047] Figure 3 The UV-Vis spectra of Congo red stock solution and Congo red filtrate in Example 1 of this invention are shown.
[0048] Figure 4 This is an electron microscope image of the inner surface of the PEEK hollow fiber loose nanofiltration membrane prepared in Example 8 of the present invention.
[0049] Figure 5 This is an electron microscope image of the inner surface of the PEEK hollow fiber loose nanofiltration membrane prepared in Example 9 of the present invention.
[0050] Figure 6 The graph shows the relationship between the water permeability, Congo red rejection rate, and sodium chloride rejection rate of the PEEK hollow fiber loose nanofiltration membranes prepared in Examples 7-10 of this invention. Detailed Implementation
[0051] To further understand the present invention, preferred embodiments of the present invention are described below. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.
[0052] This invention utilizes a "pore-forming-stretching-heat-setting" process to effectively induce and stabilize the microporous structure of fibers, ultimately obtaining high-strength, high-flux polyetheretherketone hollow fiber loose nanofiltration with precisely controllable pore size. The steps are as follows:
[0053] S1. Blending and Granulation:
[0054] 60wt%~90wt% of dried polyether ether ketone powder and 10wt%~40wt% of dried polyether imide powder are blended, and the resulting mixture is melt-extruded and granulated to obtain blended resin particles.
[0055] S2. Extrusion and cooling of precursor fibers:
[0056] The blended resin particles are fed into a hollow fiber extruder for melt extrusion, cooled and solidified, and then drawn and wound to obtain the blended precursor hollow fiber.
[0057] S3. Heat treatment (annealing):
[0058] The hollow fiber of the blend precursor was heat-treated at 220~300℃ for 1~5h to obtain annealed hollow fiber;
[0059] S4. Selective extraction for pore formation:
[0060] The annealed hollow fibers were immersed in a selective extractant and extracted for 2-48 hours. The extracted hollow fibers were then washed repeatedly by immersing them in isopropanol and deionized water, and then stored in a 10-70 wt% glycerol aqueous solution for 24-48 hours to obtain nascent polyetheretherketone hollow fibers.
[0061] The selective extractant is a mixed solution of ethanolamine and N-methylpyrrolidone, with the volume fraction of ethanolamine being 10%~30% and the volume fraction of NMP being 70%~90%.
[0062] S5. Post-stretching treatment:
[0063] First, the nascent polyetheretherketone hollow fibers are hot-stretched at 100~250℃ with a hot stretching ratio of 100~300%, then heat-set for 10~30 minutes, and then wound up to obtain a loose polyetheretherketone hollow fiber nanofiltration membrane.
[0064] Alternatively, the nascent polyetheretherketone hollow fibers are first cold-stretched at 20-25°C with a cold stretching ratio greater than 0% and less than or equal to 15%, and then cold-set for 1-5 minutes. Subsequently, they are hot-stretched at 100-250°C with a hot stretching ratio of 100-300%, and then hot-set for 10-30 minutes. The fibers are then wound up to obtain a loose polyetheretherketone hollow fiber nanofiltration membrane.
[0065] In step S1 of this invention, preferably, dry polyether ether ketone powder and dry polyether imide powder are first added to a powder mixer, and the resulting mixture is fed into a (micro) twin-screw blending extruder for melt blending, extrusion, and cooling. Then, the extruded strip resin is cut into uniform resin particles of uniform size and shape by a granulator, and then washed 3 to 5 times with deionized water and ethanol respectively, and vacuum dried to obtain blended resin particles.
[0066] In step S1 of this invention, it is preferable that the polyetheretherketone powder and the polyetherimide powder have the same mesh size, and more preferably that the particle size of both the polyetheretherketone powder and the polyetherimide powder is ≤48μm.
[0067] In step S1 of this invention, the drying temperature of polyetheretherketone powder and polyetherimide powder is preferably 120~160℃, and the drying time is 8~12h.
[0068] In step S1 of this invention, polyetheretherketone powder and polyetherimide powder are preferably co-mixed in a powder mixer for 3 to 5 times, with each mixing time being 15 to 30 seconds.
[0069] In step S1 of this invention, the melt extrusion temperature is preferably 350~400℃, more preferably 360~375℃; the screw speed of the twin-screw extruder is preferably 30~70 r / min, more preferably 30~50 r / min.
[0070] In step S1 of this invention, the length of the blended resin particles is preferably 2.5~3.5mm, and they are cut by a pelletizer with a motor speed frequency of 10~15.5Hz.
[0071] In step S1 of this invention, preferably after granulation, the resin particles are washed 3-5 times with deionized water and ethanol respectively, and then vacuum dried to obtain blended resin particles. Dust and other impurities adhering to the resin particles are washed away with deionized water, and the deionized water is washed away with ethanol.
[0072] In step S2 of this invention, the hollow fiber extruder is preferably a twin-screw extruder equipped with a suitable annular extruder head. The extruder head has an annular gap. After each section of the twin-screw extruder is heated to a suitable temperature and kept at that temperature for a period of time, the blended resin particles are fed into the feeding cylinder. The appropriate feeding speed and main machine speed are adjusted. After the hollow fibers are extruded smoothly, evenly and without impurities from the extruder head, they are cooled and solidified by air cooling. Then, a winding machine is used to collect the blended precursor hollow fibers at a certain traction winding speed.
[0073] In step S2 of this invention, the outer diameter of the die head of the hollow fiber extruder is preferably 4~6.4mm and the inner diameter is 3.4~5.6mm.
[0074] In step S2 of this invention, the temperatures of the first, second, and third zones and the die head zone of the hollow fiber extruder are preferably 250~310℃, 340~360℃, 350~370℃ and 345~365℃, respectively.
[0075] In step S2 of this invention, the preferred motor frequencies for the main motor speed and the feeding speed of the hollow fiber extruder are 10~30Hz and 8~24Hz, respectively.
[0076] In step S2 of this invention, the preferred traction and winding speed is 4.5~15m / min.
[0077] In step S2 of this invention, the preferred temperature for air cooling is room temperature.
[0078] In step S2 of this invention, the outer diameter of the hollow fiber in the blended precursor is preferably 0.6~1.2mm and the inner diameter is 0.4~0.9mm.
[0079] In step S3 of this invention, the blended precursor hollow fibers are placed in a muffle furnace and annealed above their glass transition temperature. During annealing, it is necessary to prevent the blended precursor hollow fibers from bending and shrinking; for example, the two ends of the blended precursor hollow fibers on the winding reel can be clamped.
[0080] In step S3 of this invention, during the heat treatment process, solid-liquid phase separation controlled by PEEK crystallization kinetics and PEI diffusion kinetics is used to improve the crystalline structure of PEEK and the position of PEI segments in the crystalline region, thereby enhancing the rigidity and thermal stability of the framework and providing a stable substrate for subsequent extraction and stretching. Preferably, the hollow fibers of the blend precursor are heat-treated at 260-300°C for 1-3 hours.
[0081] In step S4 of this invention, the annealed hollow fibers are immersed in a selective extractant to completely remove the PEI phase, thereby forming an initial, interconnected porous structure in the continuous PEEK framework. The extracted hollow fibers are then repeatedly washed with isopropanol and deionized water to thoroughly remove any residual extractant. Subsequently, they are stored in a 10-70 wt% glycerol aqueous solution for 24-48 hours to prevent the pores from collapsing during the drying process.
[0082] In step S4 of this invention, isopropanol and deionized water are used because isopropanol washes away the extractant, and deionized water washes away the isopropanol.
[0083] In this invention, in step S5, as follows: Figure 1As shown, the processing equipment (fiber drawing machine) used for post-stretching typically includes, in sequence, a raw yarn roller 1, a guide clamp 2, a hot stretching roller 3, a first heating channel 4, a first hot stretching roller group 5, a second heating channel 6, a second hot stretching roller group 7, and a winding device 8. The first hot stretching roller group 5 is fixed inside a first hot air box 9, and the second hot stretching roller group 7 is fixed inside a second hot air box 10. In step S5, after the nascent polyetheretherketone hollow fibers are wound onto the raw yarn roller 1 of the fiber drawing machine, the temperatures of the first and second hot air boxes 9 and 10, the rotation speeds and temperatures of the first and second hot stretching roller groups 5 and 7, the temperatures and lengths of the first and second heating channels 4 and 6, the stretching rates of hot stretching and cold stretching, and the winding speed are set. If cold stretching is performed first, followed by hot stretching, the preferred heating temperatures for the first heating channel 4, the first hot stretching roller group 5, and the first hot air box 9 are 20-25°C, and the heating temperatures for the second heating channel 6, the second hot stretching roller group 7, and the second hot air box 10 are 100-250°C. The length of the first heating channel 4 is 50-100cm, and the length of the second heating channel 6 is 150-250cm. The cold stretching rate is 3-5mm / min, and the hot stretching rate is 5-20mm / min. The entire stretching process is performed at a precise rate, and finally, a high-flux, high-strength polyetheretherketone hollow fiber loose nanofiltration membrane with precisely controllable pore size is obtained through winding and collecting. If only hot stretching is performed, the equipment can be adjusted according to the situation, such as using the above-mentioned equipment, or equipment without the first heating channel 4, the first hot stretching roller group 5, and the first hot air box 9.
[0084] The polyetheretherketone resin hollow fiber loose nanofiltration membrane prepared by the method of the present invention preferably has a porosity of 20-80% and a pore size of 0.01-0.03 μm. It can be used in the separation of dyes and salts.
[0085] The terminology used in this invention generally has the meanings commonly understood by those skilled in the art, unless otherwise stated.
[0086] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to embodiments. The embodiments described are merely specific descriptions of the claims of the present invention, and the claims include, but are not limited to, the content of the described embodiments.
[0087] Unless otherwise specified, all reagents and materials described in the following examples are commercially available; all test methods are conventional unless otherwise specified. Dry powder mixer: Lihongtai, model 22222. Miniature twin-screw blending extruder: Thermo Haake, model MINILAB. Granulator: Hongxing (Mechanical Equipment), model LQ-60. Hollow fiber extruder: Wuhan Ruiming Experimental Instrument Manufacturing Co., Ltd., model SJZS-10B.
[0088] Example 1
[0089] The method for using PEEK hollow fiber loose nanofiltration membranes involves the following steps:
[0090] S1. After drying polyetheretherketone (PEEK) powder and polyetherimide (PEI) powder with a particle size of 48 μm in an oven at 120 °C for 9 h, 180 g of PEEK powder with a particle size of 48 μm and 120 g of PEEK powder with a particle size of 48 μm were added to a dry powder mixer and stirred 5 times for 20 s each time to obtain a mixture. After the temperature of the micro twin-screw extruder reached a constant of 375 °C, the screw speed was adjusted to 50 rpm, and the mixture was fed into the micro twin-screw extruder for blending and extrusion. The extruded strip resin was granulated to a length of 3.5 mm by a granulator, washed 5 times with water and ethanol respectively, and finally the product was dried in a vacuum oven at 110 °C for 9 h to obtain uniform PEEK / PEI blend resin particles.
[0091] S2. After stabilizing the temperatures of Zone 1, Zone 2, Zone 3, and the die head of the hollow fiber extruder (with an annular extrusion head having an outer diameter of 6.4 mm and an inner diameter of 5.6 mm) to 270℃, 350℃, 360℃, and 355℃ respectively, the polyetheretherketone / polyetherimide blended resin granules are fed into the hollow fiber extruder. The feeding speed is adjusted to 18 Hz and the main machine speed is adjusted to 30 Hz. The extruded hollow fibers are cooled to 25℃ by air cooling with one side facing upwards. The drawing roller is wound up at a speed of 5 m / min to obtain polyetheretherketone / polyetherimide precursor hollow fibers with an inner diameter of 0.9 mm and an outer diameter of 1.2 mm.
[0092] S3. After the muffle furnace is heated to 260°C, the obtained polyetheretherketone / polyetherimide precursor hollow fiber with uniform wall thickness is clamped and fixed and placed in the muffle furnace for annealing for 3 hours. After cooling, the annealed polyetheretherketone / polyetherimide hollow fiber is taken out.
[0093] S4. Using a mixed solution of 20% (v / v) ethanolamine and 80% (v / v) N-methylpyrrolidone as the extractant, the annealed polyetheretherketone / polyetherimide hollow fibers were immersed in the extractant after heating to 115°C for 16 h. The extracted hollow fibers were then repeatedly washed by immersing them in isopropanol and deionized water to thoroughly remove residual extractant. Subsequently, they were soaked in a 50 wt% glycerol aqueous solution for 24 h to obtain nascent polyetheretherketone hollow fibers.
[0094] S5. The heating temperature of the second heating channel 6, the second hot air box 10, and the second hot stretching roller group 7 of the fiber drawing machine (excluding the first heating channel 4, the first hot stretching roller group 5, and the first hot air box 9) is set to 150℃. The length of the second heating channel 6 is 150cm. After the nascent polyetheretherketone hollow fibers are wound around the raw yarn roller 1, they are hot stretched at a stretching rate of 5mm / min and a stretching ratio of 100%. The fibers are then heat-set for 15min to obtain a PEEK hollow fiber loose nanofiltration membrane.
[0095] The PEEK hollow fiber loose nanofiltration membrane prepared in Example 1 was used for salt separation of a 1000 ppm sodium chloride aqueous solution containing 100 ppm Congo red. The water permeation flux of the PEEK hollow fiber loose nanofiltration membrane was measured to be 13.5 L / (m²). 2. h . The membrane exhibits a 99.9% rejection rate for Congo red and a 9.8% rejection rate for sodium chloride. With a porosity of 60% and an average pore size of 0.014 μm, the PEEK hollow fiber loose nanofiltration membrane prepared in this invention demonstrates excellent permeability selectivity in dye-salt separation systems, making it highly suitable for treating dyeing and printing wastewater containing dyes and salts.
[0096] Figure 2 This is a cross-sectional electron microscope image of the PEEK hollow fiber loose nanofiltration membrane prepared in Example 1. From... Figure 2 As can be seen, the PEEK hollow fiber loose nanofiltration membrane of the present invention has a mesh-like pore structure.
[0097] The PEEK hollow fiber loose nanofiltration membrane prepared in Example 1 was used to treat an aqueous solution containing 100 ppm Congo red (Congo red stock solution) to obtain Congo red filtrate. Figure 3 The image shows a comparison of the UV-Vis spectra of Congo red stock solution and Congo red filtrate. As can be seen from the figure, the characteristic absorption peaks of Congo red in the filtrate have completely disappeared, indicating that the PEEK hollow fiber loose nanofiltration membrane has an excellent retention effect on Congo red.
[0098] Example 2
[0099] The method for using PEEK hollow fiber loose nanofiltration membranes involves the following steps:
[0100] S1~S4. Same as in Example 1;
[0101] S5. Set the heating temperature of the first heating channel 4, the first hot air box 9, and the first hot stretching roller group 5 of the fiber drawing machine to 25℃, and the heating temperature of the second heating channel 6, the second hot air box 10, and the second hot stretching roller group 7 to 150℃. The length of the first heating channel 4 is 50cm, and the length of the second heating channel 6 is 150cm. After winding the nascent polyetheretherketone hollow fibers onto the raw yarn roller 1 of the fiber drawing machine, perform cold stretching at a stretching rate of 3mm / min and a stretching ratio of 10%, and cold set for 3min. Then perform hot stretching at a stretching rate of 5mm / min and a stretching ratio of 100%, and heat set for 15min to obtain a PEEK hollow fiber loose nanofiltration membrane.
[0102] The PEEK hollow fiber loose nanofiltration membrane described in Example 2 was used for salt separation of a 1000 ppm sodium chloride aqueous solution containing 100 ppm Congo red. The water permeation flux of the PEEK hollow fiber loose nanofiltration membrane was measured to be 14 L / (m²). 2. h . The membrane had a rejection rate of 99.8% for Congo red and 9.6% for sodium chloride. The membrane porosity was 62% and the average pore size was 0.015 μm.
[0103] Example 3
[0104] The method for using PEEK hollow fiber loose nanofiltration membranes involves the following steps:
[0105] S1. After drying polyetheretherketone (PEEK) powder and polyetherimide (PEI) powder with a particle size of 48 μm in an oven at 120℃ for 9 hours, 210 g of PEEK powder with a particle size of 48 μm and 90 g of PEEK powder with a particle size of 48 μm were added to a dry powder mixer and stirred 5 times for 20 seconds each time to obtain a mixture. After the temperature of the micro twin-screw extruder reached a constant of 375℃, the screw speed was adjusted to 50 rpm, and the mixture was fed into the micro twin-screw extruder for blending and extrusion. The extruded strip resin was granulated to a length of 3.5 mm by a granulator, washed 5 times with water and ethanol respectively, and finally the product was dried in a vacuum oven at 110℃ for 9 hours to obtain uniform PEEK / PEI blend resin particles.
[0106] S2. After stabilizing the temperatures of Zone 1, Zone 2, Zone 3, and the die head of the hollow fiber extruder (with an annular extrusion head having an outer diameter of 6.4 mm and an inner diameter of 5.6 mm) to 290℃, 360℃, 370℃, and 365℃ respectively, the polyetheretherketone / polyetherimide blended resin granules are fed into the hollow fiber extruder. The feeding speed is adjusted to 18 Hz and the main machine speed is adjusted to 30 Hz. The extruded hollow fibers are cooled by air cooling with one side facing upwards to a temperature of 25℃. The drawing roller is wound and collected at a speed of 8 m / min to obtain polyetheretherketone / polyetherimide precursor hollow fibers with an inner diameter of 0.8 mm and an outer diameter of 1.0 mm.
[0107] S3. Same as Example 1;
[0108] S4. Using a mixed solution of 20% (v / v) ethanolamine and 80% (v / v) N-methylpyrrolidone as the extractant, the annealed polyetheretherketone / polyetherimide hollow fibers were immersed in the extractant after heating to 120°C for 24 hours. The extracted hollow fibers were then repeatedly washed by immersing them in isopropanol and deionized water to thoroughly remove residual extractant. Subsequently, they were immersed in 50 wt% glycerol and 50 wt% deionized water and stored for 16 hours to obtain nascent polyetheretherketone hollow fibers.
[0109] S5. The heating temperature of the second heating channel 6, the second hot air box 10, and the second hot stretching roller group 7 of the fiber drawing machine (excluding the first heating channel 4, the first hot stretching roller group 5, and the first hot air box 9) is set to 200℃. The length of the second heating channel 6 is 150cm. After the nascent polyetheretherketone hollow fibers are wound around the raw yarn roller 1, they are hot stretched at a stretching rate of 15mm / min and a stretching ratio of 200%. The stretching is then heat-set for 25min to obtain a PEEK hollow fiber loose nanofiltration membrane.
[0110] The PEEK hollow fiber loose nanofiltration membrane described in Example 3 was used for salt separation of a 1000 ppm sodium chloride aqueous solution containing 100 ppm Congo red. The water permeation flux of the PEEK hollow fiber loose nanofiltration membrane was measured to be 13.2 L / (m²). 2. h . The membrane had a rejection rate of 99.9% for Congo Red and 9.7% for sodium chloride. The membrane had a porosity of 40% and an average pore size of 0.017 μm.
[0111] Example 4
[0112] The method for using PEEK hollow fiber loose nanofiltration membranes involves the following steps:
[0113] S1~S4. Same as Example 3;
[0114] S5. The heating temperature of the second heating channel 6, the second hot air box 10, and the second hot stretching roller group 7 of the fiber drawing machine (excluding the first heating channel 4, the first hot stretching roller group 5, and the first hot air box 9) is set to 200℃. The length of the second heating channel 6 is 250cm. After the nascent polyetheretherketone hollow fibers are wound around the raw yarn roller 1, they are hot stretched at a stretching rate of 15mm / min and a stretching ratio of 300%. After heat setting for 30min, a PEEK hollow fiber loose nanofiltration membrane is obtained.
[0115] The PEEK hollow fiber loose nanofiltration membrane described in Example 4 was used for salt separation of a 1000 ppm sodium chloride aqueous solution containing 100 ppm Congo red. The water permeation flux of the PEEK hollow fiber loose nanofiltration membrane was measured to be 17 L / (m²). 2. h . The membrane had a rejection rate of 99.6% for Congo red and 7.3% for sodium chloride. The membrane porosity was 45% and the average pore size was 0.023 μm.
[0116] Example 5
[0117] The method for using PEEK hollow fiber loose nanofiltration membranes involves the following steps:
[0118] S1. After drying polyetheretherketone (PEEK) powder and polyetherimide (PEI) powder with a particle size of 48 μm in an oven at 120℃ for 9 h, 240 g of PEEK powder with a particle size of 48 μm and 60 g of PEEK powder with a particle size of 48 μm were added to a dry powder mixer and stirred 5 times for 20 s each time to obtain a mixture. After the temperature of the micro twin-screw blending extruder reached a constant of 375℃, the screw speed was adjusted to 50 rpm, and the mixture was fed into the micro twin-screw blending extruder for blending and extrusion. The extruded strip resin was granulated to a length of 3.5 mm by a granulator, washed 5 times with water and ethanol respectively, and finally the product was dried in a vacuum oven at 110℃ for 9 h to obtain uniform PEEK / PEI blended resin particles.
[0119] S2. After stabilizing the temperatures of Zone 1, Zone 2, Zone 3, and the die head of the hollow fiber extruder (with an annular extrusion head having an outer diameter of 6.4 mm and an inner diameter of 5.6 mm) to 290℃, 360℃, 375℃, and 370℃ respectively, the polyetheretherketone / polyetherimide blended resin granules are fed into the hollow fiber extruder. The feeding speed is adjusted to 18 Hz and the main machine speed is adjusted to 30 Hz. The extruded hollow fibers are cooled by air cooling from one side upwards to a temperature of 25℃. The drawing roller is wound and collected at a speed of 15 m / min to obtain polyetheretherketone / polyetherimide precursor hollow fibers with an inner diameter of 0.4 mm and an outer diameter of 0.6 mm.
[0120] S3. Same as Example 1;
[0121] S4. Using a mixed solution of 20% (v / v) ethanolamine and 80% (v / v) N-methylpyrrolidone as the extractant, the temperature was raised to 125°C. The annealed polyetheretherketone / polyetherimide hollow fibers were then immersed in the extractant and extracted for 30 h. The extracted hollow fibers were then repeatedly washed by immersing them in isopropanol and deionized water to thoroughly remove any residual extractant. Subsequently, they were stored in a 50 wt% glycerol aqueous solution for 16 h.
[0122] S5. Set the heating temperature of the first heating channel 4, the first hot air box 9, and the first hot stretching roller group 5 of the fiber drawing machine to 25℃, and the heating temperature of the second heating channel 6, the second hot air box 10, and the second hot stretching roller group 7 to 200℃. The length of the first heating channel 4 is 70cm, and the length of the second heating channel 6 is 250cm. After winding the nascent polyetheretherketone hollow fibers onto the raw yarn roller 1 of the fiber drawing machine, perform cold stretching at a stretching rate of 3mm / min and a stretching ratio of 10%, and cold set for 3min. Then perform hot stretching at a stretching rate of 15mm / min and a stretching ratio of 300%, and heat set for 30min to obtain a PEEK hollow fiber loose nanofiltration membrane.
[0123] The PEEK hollow fiber loose nanofiltration membrane described in Example 5 was used for salt separation of a 1000 ppm sodium chloride aqueous solution containing 100 ppm Congo red. The water permeation flux of the PEEK hollow fiber loose nanofiltration membrane was measured to be 10.0 L / (m²). 2. h . The membrane had a rejection rate of 99.9% for Congo Red and 9.7% for sodium chloride. The membrane porosity was 30% and the average pore size was 0.023 μm.
[0124] Example 6
[0125] The method for using PEEK hollow fiber loose nanofiltration membranes involves the following steps:
[0126] S1~S4. Same as in Example 1;
[0127] S5. Set the heating temperature of the first heating channel 4, the first hot air box 9, and the first hot stretching roller group 5 of the fiber drawing machine to 25℃, and the heating temperature of the second heating channel 6, the second hot air box 10, and the second hot stretching roller group 7 to 200℃. The length of the first heating channel 4 is 70cm, and the length of the second heating channel 6 is 250cm. After winding the nascent polyetheretherketone hollow fibers onto the raw yarn roller 1 of the fiber drawing machine, perform cold stretching at a stretching rate of 3mm / min and a stretching ratio of 10%, and cold set for 3min. Then perform hot stretching at a stretching rate of 15mm / min and a stretching ratio of 300%, and heat set for 30min to obtain a PEEK hollow fiber loose nanofiltration membrane.
[0128] The PEEK hollow fiber loose nanofiltration membrane described in Example 6 was used for salt separation of a 1000 ppm sodium chloride aqueous solution containing 100 ppm Congo red. The water permeation flux of the PEEK hollow fiber loose nanofiltration membrane was measured to be 25 L / (m²). 2. h . The membrane had a rejection rate of 98% for Congo red and 4.1% for sodium chloride. The membrane porosity was 80% and the average pore size was 0.030 μm.
[0129] Example 7
[0130] The method for using PEEK hollow fiber loose nanofiltration membranes involves the following steps:
[0131] S1~S4. Same as in Example 1;
[0132] S5. Setting up a fiber drawing machine: The heating temperature of the second hot air box 10 and the second hot stretching roller group 7 of the fiber drawing machine (excluding the first heating channel 4, the first hot stretching roller group 5 and the first hot air box 9) is 250℃. The length of the second heating channel 6 is 150cm. After the nascent polyether ether ketone hollow fibers are wound around the raw yarn roller 1 of the fiber drawing machine, they are hot stretched at a stretching rate of 5mm / min and a stretching ratio of 100%. After heat setting for 15min, a PEEK hollow fiber loose nanofiltration membrane is obtained.
[0133] The PEEK hollow fiber loose nanofiltration membrane described in Example 7 was used for salt separation of a 1000 ppm sodium chloride aqueous solution containing 100 ppm Congo red. The water permeation flux of the PEEK hollow fiber loose nanofiltration membrane was measured to be 13.1 L / (m²). 2. h . The membrane had a rejection rate of 99.9% for Congo Red and 9.7% for sodium chloride. The membrane porosity was 55% and the average pore size was 0.010 μm.
[0134] Example 8
[0135] The method for using PEEK hollow fiber loose nanofiltration membranes involves the following steps:
[0136] S1~S4. Same as in Example 1;
[0137] S5. Setting up a fiber drawing machine: The heating temperature of the second hot air box 10 and the second hot stretching roller group 7 of the fiber drawing machine (excluding the first heating channel 4, the first hot stretching roller group 5 and the first hot air box 9) is 250℃. The length of the second heating channel 6 is 200cm. After the nascent polyether ether ketone hollow fibers are wound around the raw yarn roller 1 of the fiber drawing machine, they are hot stretched at a stretching rate of 10mm / min and a stretching ratio of 150%. After heat setting for 20min, a PEEK hollow fiber loose nanofiltration membrane is obtained.
[0138] The PEEK hollow fiber loose nanofiltration membrane described in Example 8 was used for salt separation of a 1000 ppm sodium chloride aqueous solution containing 100 ppm Congo red. The water permeation flux of the PEEK hollow fiber loose nanofiltration membrane was measured to be 16.2 L / (m²). 2. h . The membrane had a rejection rate of 99.6% for Congo red and 7.2% for sodium chloride. The membrane porosity was 57% and the average pore size was 0.013 μm.
[0139] Example 9
[0140] The method for using PEEK hollow fiber loose nanofiltration membranes involves the following steps:
[0141] S1~S4. Same as in Example 1;
[0142] S5. Setting up a fiber drawing machine: The heating temperature of the second hot air box 10 and the second hot stretching roller group 7 of the fiber drawing machine (excluding the first heating channel 4, the first hot stretching roller group 5 and the first hot air box 9) is 250℃. The length of the second heating channel 6 is 250cm. After the nascent polyether ether ketone hollow fibers are wound around the raw yarn roller 1 of the fiber drawing machine, they are hot stretched at a stretching rate of 15mm / min and a stretching ratio of 200%. After heat setting for 25min, a PEEK hollow fiber loose nanofiltration membrane is obtained.
[0143] The PEEK hollow fiber loose nanofiltration membrane described in Example 9 was used for salt separation of a 1000 ppm sodium chloride aqueous solution containing 100 ppm Congo red. The water permeation flux of the PEEK hollow fiber loose nanofiltration membrane was measured to be 20.1 L / (m²). 2. h . The membrane had a rejection rate of 99.3% for Congo Red and 5.1% for sodium chloride. The membrane porosity was 65% and the average pore size was 0.017 μm.
[0144] Example 10
[0145] The method for using PEEK hollow fiber loose nanofiltration membranes involves the following steps:
[0146] S1~S4. Same as in Example 1;
[0147] S5. Set the heating temperature of the first heating channel 4, the first hot air box 9, and the first hot stretching roller group 5 of the fiber drawing machine to 25℃, and the heating temperature of the second heating channel 6, the second hot air box 10, and the second hot stretching roller group 7 to 250℃. The length of the first heating channel 4 is 70cm, and the length of the second heating channel 6 is 250cm. After winding the nascent polyetheretherketone hollow fibers onto the raw yarn roller 1 of the fiber drawing machine, perform cold stretching at a stretching rate of 3mm / min and a stretching ratio of 10%, and then perform hot stretching at a stretching rate of 15mm / min and a stretching ratio of 200%. Heat set for 25min to obtain a PEEK hollow fiber loose nanofiltration membrane.
[0148] The PEEK hollow fiber loose nanofiltration membrane from Example 10 was used for salt separation of a 1000 ppm sodium chloride aqueous solution containing 100 ppm Congo red. The water permeation flux of the PEEK hollow fiber loose nanofiltration membrane was measured to be 20.7 L / (m²). 2. h . The membrane had a rejection rate of 99.2% for Congo Red and 4.9% for sodium chloride. The membrane porosity was 66% and the average pore size was 0.018 μm.
[0149] Figure 4 The image shows an internal surface electron microscope image of the PEEK hollow fiber loose nanofiltration membrane prepared in Example 8 of the present invention. It can be seen that after the post-stretching treatment, the pore structure is stretched into an elliptical shape, which gives it better flux and more flexible pore adjustment space.
[0150] Figure 5 The image shows an internal surface electron microscope image of the PEEK hollow fiber loose nanofiltration membrane prepared in Example 9 of the present invention. It can be seen that after the post-stretching treatment, the circular pore structure is further elongated into a slit-shaped nanopore structure at a higher stretching magnification.
[0151] Figure 6 The graph shows the relationship between the water permeability, Congo red rejection rate, and sodium chloride rejection rate of the PEEK hollow fiber loose nanofiltration membranes prepared in Examples 7-10 of this invention. Figure 6 As the stretching ratio increases, the water permeability of the PEEK hollow fiber loose nanofiltration membrane gradually increases, while the salt rejection rate gradually decreases.
[0152] Obviously, the above embodiments are merely examples for clear illustration and are not intended to limit the embodiments. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all embodiments here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.
Claims
1. A method for preparing a polyetheretherketone resin hollow fiber loose nanofiltration membrane, characterized in that, The steps are as follows: S1. Blending and Granulation: 60wt%~90wt% of dried polyether ether ketone powder and 10wt%~40wt% of dried polyether imide powder are blended, and the resulting mixture is melt-extruded and granulated to obtain blended resin particles. S2. Extrusion and cooling of precursor fibers: The blended resin particles are fed into a hollow fiber extruder for melt extrusion, cooled and solidified, and then drawn and wound to obtain the blended precursor hollow fiber. S3. Heat treatment: The hollow fiber of the blend precursor was heat-treated at 220~300℃ for 1~5h to obtain annealed hollow fiber; S4. Selective extraction for pore formation: Annealed hollow fibers are immersed in a selective extractant and extracted for 2-48 hours. The extracted hollow fibers are then washed repeatedly by immersing them in isopropanol and deionized water, and then stored in a 10wt%-70wt% glycerol aqueous solution for 24-48 hours to obtain nascent polyetheretherketone hollow fibers. The selective extractant is a mixed solution of ethanolamine and N-methylpyrrolidone, wherein the volume fraction of ethanolamine is 10% to 30% and the volume fraction of N-methylpyrrolidone is 70% to 90%. S5. Post-stretching treatment: First, the nascent polyetheretherketone hollow fibers are hot-stretched at 100~250℃ with a hot stretching ratio of 100~300%, then heat-set for 10~30 minutes, and then wound up to obtain a loose polyetheretherketone hollow fiber nanofiltration membrane. Alternatively, the nascent polyetheretherketone hollow fibers are first cold-stretched at 20-25°C with a cold stretching ratio greater than 0% and less than or equal to 15%, and then cold-set for 1-5 minutes. Subsequently, they are hot-stretched at 100-250°C with a hot stretching ratio of 100-300%, and then hot-set for 10-30 minutes. The fibers are then wound up to obtain a loose polyetheretherketone hollow fiber nanofiltration membrane.
2. The method for preparing the polyetheretherketone resin hollow fiber loose nanofiltration membrane according to claim 1, characterized in that, In step S1, one or more of the following characteristics are present: The polyetheretherketone powder and the polyetherimide powder have the same mesh size; The drying temperatures are each independently between 120 and 160°C; The drying time is 8-12 hours, each independently. The polyetheretherketone powder and polyetherimide powder are co-mixed in a powder mixer for 3 to 5 times, with each mixing time being 15 to 30 seconds. The temperature of the melt extrusion is 350~400℃; The length of the blended resin particles is 2.5~3.5mm; After granulation, the mixture is washed 3-5 times with deionized water and ethanol respectively, and then vacuum dried to obtain blended resin particles.
3. The method for preparing the polyetheretherketone resin hollow fiber loose nanofiltration membrane according to claim 2, characterized in that, The particle size of both the polyetheretherketone powder and the polyetherimide powder is ≤48μm. The temperature of the melt extrusion is 360~375℃.
4. The method for preparing the polyetheretherketone resin hollow fiber loose nanofiltration membrane according to claim 1, characterized in that, In step S2, one or more of the following characteristics are present: The outer diameter of the die head of the hollow fiber extruder is 4~6.4mm, and the inner diameter is 3.4~5.6mm; The temperatures of the first, second, and third zones and the die head zone of the hollow fiber extruder are 250~310℃, 340~360℃, 350~370℃ and 345~365℃, respectively; The motor frequencies of the main machine speed and the feeding speed of the hollow fiber extruder are 10~30Hz and 8~24Hz, respectively; Air cooling is used for curing, with the air cooling temperature being 20~25℃; The traction winding speed is 4.5~15m / min; The hollow fibers in the blended precursor have an outer diameter of 0.6~1.2mm and an inner diameter of 0.4~0.9mm.
5. The method for preparing the polyetheretherketone resin hollow fiber loose nanofiltration membrane according to claim 1, characterized in that, In step S3, the hollow fibers of the blend precursor are heat-treated at 260~300℃ for 1~3 hours.
6. The method for preparing the polyetheretherketone resin hollow fiber loose nanofiltration membrane according to claim 1, characterized in that, In step S5, the cold stretching rate is 3~5 mm / min, and the hot stretching rate is 5~20 mm / min.
7. A polyetheretherketone resin hollow fiber loose nanofiltration membrane prepared by the method for preparing a polyetheretherketone resin hollow fiber loose nanofiltration membrane according to any one of claims 1 to 6.
8. The polyetheretherketone resin hollow fiber loose nanofiltration membrane according to claim 7, characterized in that, The porosity of the polyetheretherketone resin hollow fiber loose nanofiltration membrane is 20-80%, and the average pore size is 0.01-0.03 μm.
9. The application of the polyetheretherketone resin hollow fiber loose nanofiltration membrane according to claim 8 in the separation of dyes and salts.
Citation Information
Patent Citations
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CN108499369A