Porous membrane and method for manufacturing the same

Patent metadata

Field	Value
Publication number	US-9314745-B2
Application number	US-201314380551-A
Country	US
Kind code	B2
Filing date	Mar 28, 2013
Priority date	Mar 30, 2012
Publication date	Apr 19, 2016
Grant date	Apr 19, 2016

Abstract

Disclosed are a porous membrane having improved water permeability and elongation at break as well as high mechanical strength and impurity rejection rate and a method for manufacturing the same. The porous membrane of the present invention comprises a symmetric bead structure comprising a plurality of spherical crystallites. Each of the plurality of spherical crystallites comprises a plurality of sub-spherical crystallites.

First claim

The invention claimed is:

1. A porous membrane comprising a symmetric bead structure comprising a plurality of spherical crystallites,
wherein each of the plurality of spherical crystallites comprises a plurality of sub-spherical crystallites.

2. The porous membrane of claim 1 , wherein the plurality of spherical crystallites comprise polyvinylidene difluoride.

3. The porous membrane of claim 2 , wherein the plurality of spherical crystallites further comprise zeolite.

4. The porous membrane of claim 1 , wherein water permeability of the porous membrane measured under nitrogen pressure of 1.0 to 3.0 kgf/cm 2 is 0.7 (ml/cm 2 )·(min) −1 ·(kgf/cm 2 ) −1 or more, and
wherein compaction index of the porous membrane as defined by a following equation is 0.5 or less:
CI=( Lp 1.0 −Lp 3.0 )/ Lp 1.0   [Equation]

wherein ‘CI’ represents the compaction index, ‘Lp 1.0 ’ represents water permeability of the porous membrane measured under a nitrogen pressure of 1.0 kgf/cm 2 , and ‘Lp 3.0 ’ represents water permeability of the porous membrane measured under a nitrogen pressure of 3.0 kgf/cm 2 .

5. The porous membrane of claim 1 , wherein the porous membrane has tensile strength of 0.7 kgf/fiber or more and elongation at break of 50% or more, and
wherein rejection rate of the porous membrane with respect to particles having a diameter of 0.1 μm is 90% or more.

6. A method for manufacturing a porous membrane, the method comprising:
dissolving at least one polymer selected from the group consisting of polyethersulfone, polysulfone, and polyvinylidene difluoride in a poor solvent to prepare a basic solution;
adding an ionic liquid to the basic solution to prepare a spinning dope;
extruding the spinning dope through a spinneret; and
bringing the extruded spinning dope into contact with a coagulation solution so as to form a porous structure; wherein the membrane comprises a symmetric bead structure comprising a plurality of spherical crystallites,
wherein each of the plurality of spherical crystallites comprises a plurality of sub-spherical crystallites.

7. The method of claim 6 , wherein the at least one polymer is dissolved in the poor solvent at a temperature of 100° C. or more but below a boiling point of the poor solvent.

8. The method of claim 6 , wherein the poor solvent comprises at least one of cyclohexanone, isophorone, γ-butyrolactone, methyl isoamyl ketone, dimethyl phthalate, propylene glycol methyl ether, propylene carbonate, diacetone alcohol, and glycerol triacetate.

9. The method of claim 8 , wherein the poor solvent comprises γ-butyrolactone.

10. The method of claim 6 , wherein the basic solution comprises 20 to 40% by weight of the at least one polymer and 60 to 80% by weight of the poor solvent, and
wherein the spinning dope is prepared by adding the ionic liquid to the basic solution in an amount of 2 to 20% by weight based on total weight of the at least one polymer.

11. The method of claim 6 , wherein the ionic liquid comprises 1-butyl-3-methylimidazolium tetrafluoroborate.

12. The method of claim 6 , further comprising adding zeolite to the basic solution.

13. The method of claim 6 , wherein the coagulation solution comprises 20 to 80% by weight of water and 20 to 80% by weight of a volatile organic solvent, and
wherein the volatile organic solvent comprises at least one of methanol, ethanol, isopropyl alcohol, acetone, butanone, diacetyl, acetylacetone, hexane-2,5-dione, diethyl ether, diisopropyl ether, and polyether.

14. The method of claim 6 , wherein a temperature of the coagulation solution is maintained at 5 to 20° C.

Assignees

• Kolon Inc

Inventors

• Ryu Jae Hee
• Shin Yong-Cheol
• Lee Jae Hun

Classifications

• B01D69/02 Primary

  characterised by their properties · CPC title

• B01D71/028

  Molecular sieves (carbon B01D71/021) · CPC title

• B01D67/0016

  Coagulation · CPC title

• B01D2325/02

  Details relating to pores or porosity of the membranes · CPC title

• B01D69/087

  Details relating to the spinning process · CPC title