Method for preparing block copolymer hollow fiber membrane by melt spinning-stretching and selective swelling

Patent metadata

Field	Value
Publication number	US-11766640-B2
Application number	US-202218001092-A
Country	US
Kind code	B2
Filing date	Mar 23, 2022
Priority date	Mar 24, 2021
Publication date	Sep 26, 2023
Grant date	Sep 26, 2023

Abstract

The disclosure provides a method for preparing a hollow fiber membrane by melt spinning-stretching and selective swelling, including: preparing a nascent hollow fiber by melt spinning in an inert gas protective atmosphere by using an amphiphilic block copolymer as a film forming material, and stretching the nascent hollow fiber in the cooling process, a stretch rate being controlled at 200-540 mm/min, and a stretch ratio being controlled at 150-600%; immersing the obtained hollow fiber in a swelling solvent, and treating the hollow fiber in a water bath at 65° C. for 1 h; and then transferring the hollow fiber into a long-chain alkane solvent, treating the hollow fiber at the same temperature for 1-12 h, and after the completion of the treatment, immediately taking out the hollow fiber and drying the hollow fiber to obtain the hollow fiber membrane with a bicontinuous porous structure. By combining the melt spinning-stretching and the selective swelling, the method of the disclosure can synchronously and continuously improve the permeability and selectivity of the hollow fiber membrane. The treatment in the long-chain alkane solvent can make the polar chain excessively enriched on the surface of the membrane migrate inward, thereby improving the performance of the hollow fiber membrane.

First claim

The invention claimed is:

1. A method for preparing a hollow fiber membrane by melt spinning-stretching and selective swelling, comprising:
1) preparing a nascent hollow fiber by melt spinning in an inert gas protective atmosphere by using an amphiphilic block copolymer as a film forming material, and stretching the nascent hollow fiber in a cooling process, a stretch rate being controlled at 250-500 mm/min, and a stretch ratio being controlled at 300-550%; the amphiphilic block copolymer in 1) is composed of block A and block B (A-B), wherein the block A is selected from any one of polysulfone (PSF), polyethersulfone (PES), polyphenylsulfone (PPSU) and polylactic acid (PLA), the block B is selected from any one of polyethylene glycol (PEG) and polyethylene oxide (PEO), and the amphiphilic block copolymer has a total molecular weight of 50-200 kDa;
2) immersing the hollow fiber obtained in 1) in a swelling solvent, and treating the hollow fiber in a water bath at 65° C. for 1 h; and then transferring the hollow fiber into a long-chain alkane solvent, treating the hollow fiber at 65° C. for 1-12 h, and after the treating the hollow fiber at 65° C. for 1-12 h, immediately taking out the hollow fiber and drying the hollow fiber to obtain the hollow fiber membrane with a bicontinuous porous structure, wherein
the long-chain alkane solvent in 2) is any one or a mixture of two or more of n-pentane, n-hexane, n-heptane, n-octane, n-nonane and n-decane.

2. The method according to claim 1 , wherein the block A is polysulfone (PSF), and the block B is polyethylene glycol (PEG).

3. The method according to claim 2 , wherein the amphiphilic block copolymer and molecular weight thereof is selected from any one of PSF 75 -PEG 20 , PES 73 -PEG 19 , PPSU 78 -PEG 22 and PLA 75 -PEO 21 , in kDa.

4. The method according to claim 1 , wherein the process of the melt spinning in 1) includes melting a solid amphiphilic block copolymer and then extruding the melted amphiphilic block copolymer with a single-screw or twin-screw extruder through a spinneret to obtain the hollow fiber.

5. The method according to claim 4 , wherein the solid amphiphilic block copolymer is melted at a temperature of 100-250° C.

6. The method according to claim 4 , wherein the solid amphiphilic block copolymer is melted at a temperature of 200-210° C.

7. The method according to claim 4 , wherein in the melting, an inert protective gas, comprising nitrogen or helium, is used to prevent the amphiphilic block copolymer from being oxidized or degraded.

8. The method according to claim 1 , wherein the cooling process in 1) is as follows: cooling the nascent hollow fiber membrane by water cooling, air cooling or natural cooling after being obtained through a spinneret.

9. The method according to claim 1 , wherein the swelling solvent in 2) is a mixed solvent composed of n-propanol and a polar solvent, and the polar solvent accounts for 0-50 wt % of the mixed solvent.

10. The method according to claim 9 , wherein the polar solvent accounts for 10 wt %-25 wt % of the mixed solvent.

11. The method according to claim 9 , wherein the polar solvent is selected from any one of acetone, tetrahydrofuran or toluene.

12. The method according to claim 9 , wherein the swelling solvent is an n-propanol/acetone mixed solvent containing 20 wt % of acetone, an n-propanol/tetrahydrofuran mixed solvent containing 20 wt % of tetrahydrofuran, or an n-propanol/toluene mixed solvent containing 10 wt % of toluene.

13. The method according to claim 1 , wherein the long-chain alkane solvent in 2) is n-heptane.

14. The method according to claim 1 , wherein the treatment in the long-chain alkane solvent in 2) is carried out for 1 h, 6 h or 12 h.

15. A method for preparing a hollow fiber membrane by melt spinning-stretching and selective swelling, specifically comprising the following:
1) melt spinning-stretching process comprising
melting a solid amphiphilic block copolymer by heating at a temperature of 100-250° C. to obtain a molten polymer, extruding the molten polymer with a single-screw or twin-screw extruder through a spinneret in an inert gas protective atmosphere to obtain a nascent hollow fiber, and stretching the nascent hollow fiber in a cooling process, a stretch rate being controlled at 250-500 mm/min, and a stretch ratio being controlled at 300-550%; wherein the solid amphiphilic block copolymer is composed of block A and block B (A-B), wherein the block A is selected from polysulfone (PSF), and the block B is selected from any one of polyethylene glycol (PEG) and polyethylene oxide (PEO); the block B accounts for 10-40% of the total mass of the solid amphiphilic block copolymer; the solid amphiphilic block copolymer has a total molecular weight of 50-200 kDa; and
2) pore forming process by selective swelling comprising
placing the amphiphilic block copolymer hollow fiber obtained in 1) in a container filled with a swelling solvent, treating the hollow fiber in a water bath at 65° C. for 1 h to form a porous structure, then transferring the hollow fiber into a long-chain alkane solvent and treating the hollow fiber for 1-12 h, and finally, drying the hollow fiber to obtain the hollow fiber membrane with a bicontinuous porous structure, wherein
the long-chain alkane solvent in 2) is any one or a mixture of two or more of n-pentane, n-hexane, n-heptane, n-octane, n-nonane and n-decane.

Assignees

• Nanjing University Of Technology

Inventors

• Wang Yong
• Zhong Dinglei
• Zhou Jiemei

Classifications

• B01D67/0027 Primary

  by stretching · CPC title

• B01D67/002

  from melts · CPC title

• B01D69/08

  Hollow fibre membranes (manufacture of hollow fibres D01D5/24, D01F1/08) · CPC title

• B01D71/5211

  Polyethylene glycol or polyethyleneoxide · CPC title

• B01D71/68

  Polysulfones; Polyethersulfones · CPC title