Thermally rearranged poly(benzoxazoleco-imide) separation membrane for membrane distillation and fabrication method thereof

Patent metadata

Field	Value
Publication number	US-10071346-B2
Application number	US-201414917759-A
Country	US
Kind code	B2
Filing date	Sep 3, 2014
Priority date	Sep 26, 2013
Publication date	Sep 11, 2018
Grant date	Sep 11, 2018

Abstract

The present invention relates to the production of a hydroxyl polyimide-co-polyimide membrane, the fabrication of a thermally rearranged poly(benzoxazole-co-imide) membrane by thermally treating the hydroxyl polyimide-co-polyimide membrane, and the application of the thermally rearranged poly(benzoxazole-co-imide) membrane to membrane distillation. The thermally rearranged poly(benzoxazole-co-imide) separation membrane has high liquid entry pressure, low thermal conductivity, high permeate flux, and good long-term stability, as well as excellent thermal and chemical properties. Due to these advantages, the copolymer separation membrane can be applied to membrane distillation processes.

First claim

The invention claimed is:

1. A thermally rearranged poly(benzoxazole-co-imide) separation membrane for membrane distillation, the copolymer being represented by Formula 1:

(wherein each Ar 1 is an aromatic cyclic group selected from substituted or unsubstituted tetravalent C 6 -C 24 arylene groups and substituted or unsubstituted tetravalent C 4 -C 24 heterocyclic groups, the aromatic cyclic group being a monocyclic or fused aromatic ring, or is a combination of two or more aromatic cyclic groups linked through a single bond, O, S, CO, SO 2 , Si(CH 3 ) 2 , (CH 2 ) p (1≤p≤10), (CF 2 ) q (1≤q≤10), C(CH 3 ) 2 , C(CF 3 ) 2 or CO—NH, Ar 2 is an aromatic cyclic group selected from substituted or unsubstituted divalent C 6 -C 24 arylene groups and substituted or unsubstituted divalent C 4 -C 24 heterocyclic groups, the aromatic cyclic group being a monocyclic or fused aromatic ring, or is a combination of two or more aromatic cyclic groups linked through a single bond, O, S, CO, SO 2 , Si(CH 3 ) 2 , (CH 2 ) p (1≤p≤10), (CF 2 ) q (1≤q≤10), C(CH 3 ) 2 , C(CF 3 ) 2 or CO—NH, Q represents a single bond or is O, S, CO, SO 2 , Si(CH 3 ) 2 , (CH 2 ) p (1≤p≤10), (CF 2 ) q (1≤q≤10), C(CH 3 ) 2 , C(CF 3 ) 2 , CO—NH, C(CH 3 )(CF 3 ) or a substituted or unsubstituted phenylene group, and x and y represent the mole fractions of the corresponding repeating units and satisfy 0.1≤x≤0.9, 0.1≤y≤0.9, and x+y=1)), and
wherein the thermally rearranged poly(benzoxazole-co-imide) separation membrane is a composite membrane comprising a coating layer of hydroxyl polyimide-co-polyimide nanoparticles formed on the electrospun membrane of hydroxyl polyimide-co-polyimide represented by General Formula 1:

wherein Ar 1 , Ar 2 , Q, x, and y are as defined in Formula 1).

2. The thermally rearranged poly(benzoxazole-co-imide) separation membrane according to claim 1 , wherein, in Formula 1, each Ar 1 is selected from the group consisting of the following structures:

wherein X 1 , X 2 , X 3 , and X 4 are identical to or different from each other and are each independently O, S, CO, SO 2 , Si(CH 3 ) 2 , (CH 2 ) p (1≤p≤10), (CF 2 ) q (1≤q≤10), C(CH 3 ) 2 , C(CF 3 ) 2 or CO—NH, W 1 and W 2 are identical to or different from each other and are each independently O, S, or CO, Z 1 is O, S, CR 1 R 2 or NR 3 (where R 1 , R 2 , and R 3 are identical to or different from each other and are each independently hydrogen or C 1 -C 5 alkyl), Z 2 and Z 3 are identical to or different from each other and are each independently N or CR 4 (where R 4 is hydrogen or C 1 -C 5 alkyl), with the proviso that Z 2 and Z 3 are not simultaneously CR 4 .

3. The thermally rearranged poly(benzoxazole-co-imide) separation membrane according to claim 2 , wherein, in Formula 1, each Ar 1 is selected from the group consisting of the following structures:

4. The thermally rearranged poly(benzoxazole-co-imide) separation membrane according to claim 1 , wherein, in Formula 1, Ar 2 is selected from the group consisting of the following structures:

wherein X 1 , X 2 , X 3 , and X 4 are identical to or different from each other and are each independently O, S, CO, SO 2 , Si(CH 3 ) 2 , (CH 2 ) p (1≤p≤10), (CF 2 ) q (1≤q≤10), C(CH 3 ) 2 , C(CF 3 ) 2 or CO—NH, W 1 and W 2 are identical to or different from each other and are each independently O, S or CO, and Z 1 is O, S, CR 1 R 2 or NR 3 (where R 1 , R 2 , and R 3 are identical to or different from each other and are each independently hydrogen or C 1 -C 5 alkyl), Z 2 and Z 3 are identical to or different from each other and are each independently N or CR 4 (where R 4 is hydrogen or C 1 -C 5 alkyl), with the proviso that Z 2 and Z 3 are not simultaneously CR 4 .

5. A method for fabricating the thermally rearranged poly(benzoxazole-co-imide) separation membrane according to claim 1 , the method comprising i) reacting an acid dianhydride, an ortho-hydroxydiamine, and an aromatic diamine to obtain a polyamic acid solution, followed by azeotropic thermal imidization to synthesize a hydroxyl polyimide-co-polyimide, ii) dissolving the hydroxyl polyimide-co-polyimide in an organic solvent and electrospinning the polymer solution to obtain a hydroxyl polyimide-co-polyimide membrane, and iii) thermally rearranging the hydroxyl polyimide-co-polyimide membrane.

6. The method according to claim 5 , wherein the ortho-hydroxydiamine used in step i) is represented by Formula 3:

(wherein Q is as defined in Formula 1).

7. The method according to claim 5 , wherein, in step i), the azeotropic thermal imidization is carried out in such a manner that toluene or xylene is added to the polyamic acid solution and the polyamic acid is subjected to an imidization reaction with stirring at 180 to 200° C. for 6 to 8 hours.

8. The method according to claim 5 , further comprising ii)-(a) forming a coating layer of hydroxyl polyimide-co-polyimide nanoparticles after step ii).

9. The method according to claim 8 , wherein the hydroxyl polyimide-co-polyimide nanoparticles are formed by dissolving a hydroxyl polyimide-co-polyimide and polyvinylpyrrolidone (PVP) or polyvinyl alcohol (PVA) as a dispersant in a solvent to obtain a polymer solution, dropping a non-solvent into the polymer solution, stirring the mixture, and depositing precipitates.

10. The method according to claim 9 , wherein the solvent is selected from the group consisting of N-methylpyrrolidone (NMP), dimethylacetamide (DMAc), dimethylformamide (DMF), and dimethyl sulfoxide (DMSO).

11. The method according to claim 9 , wherein the non-solvent is selected from the group consisting of water, methanol, ethanol, isopropyl alcohol, and acetone.

12. The method according to claim 9 , wherein the polymer solution contains 2 to 5% by weight of the hydroxyl polyimide-co-polyimide.

13. The method according to claim 9 , wherein the polymer solution contains 2 to 5% by weight of the polyvinylpyrrolidone (PVP) or polyvinyl alcohol (PVA).

14. The method according to claim 9 , wherein the non-solvent is dropped at a rate of 0.05 to 1 mL/min.

15. The method according to claim 9 , wherein the stirring rate is adjusted to 300 to 1,000 rpm.

16. The method according to claim 9 , wherein the hydroxyl polyimide-co-polyimide nanoparticles are formed at 20 to 100° C.

17. The method according to claim 8 , wherein the coating layer is formed by spray coating.

18. The method according to claim 5 , wherein in step iii), the thermal rearrangement is performed by heating the hydroxyl polyimide-co-polyimide membrane to 350 to 450° C. at a rate of 3°

Assignees

• Iucf Hyu

Inventors

• Lee Young Moo
• Lee So Young
• Kim Ji Hoon
• Lee Moonjoo
• Lee Wonhyo

Classifications

• B01D71/64 Primary

  Polyimides; Polyamide-imides; Polyester-imides; Polyamide acids or similar polyimide precursors · CPC title

• B82Y30/00

  Nanotechnology for materials or surface science, e.g. nanocomposites · CPC title

• C08G73/1071

  Wholly aromatic polyimides containing oxygen in the form of ether bonds in the main chain · CPC title

• B01D67/0083

  Thermal after-treatment · CPC title

• B01D71/62

  Polycondensates having nitrogen-containing heterocyclic rings in the main chain · CPC title