Hollow fiber membrane and manufacturing method thereof

1. A hollow fiber membrane having an outer surface and an inner surface, wherein the inner surface has a zebra stripe pattern having a dense portion and a porous portion alternately formed in a longitudinal direction thereof and the outer surface has a maximum pore size of about 1 μm or less, and wherein the hollow fiber membrane has a water permeability (flux) of about 1,300 LMH/bar to about 5,000 LMH/bar.

2. The hollow fiber membrane according to claim 1 , wherein the hollow fiber membrane has an average pore diameter of about 0.08 μm to about 0.3 μm and the outer surface of the hollow fiber membrane has a maximum pore size of about 0.09 μm to about 0.5 μm.

3. The hollow fiber membrane according to claim 1 , wherein, the dense portion of the inner surface has an average pore diameter of about 0.001 μm to about 0.05 μm and the porous portion of the inner surface has an average pore diameter of about 0.1 μm to about 0.55 μm.

4. The hollow fiber membrane according to claim 1 , wherein, in an area of about 5 μm 2 on the inner surface of the hollow fiber membrane, the dense portion has a maximum pore size of less than about 0.08 μm and the porous portion has at least one pore having a pore diameter of about 0.1 μm or more.

5. The hollow fiber membrane according to claim 1 , wherein the dense portion and the porous portion are formed in an apparent area ratio represented by Equation 1:

about 0.25≤apparent area ratio( B/A )≤about 2.5,

where B indicates an apparent area of the porous portion and A indicates an apparent area of the dense portion.

6. The hollow fiber membrane according to claim 1 , wherein a pore size of the hollow fiber membrane gradually increases from the outer surface thereof to the inner surface thereof.

7. The hollow fiber membrane according to claim 1 , wherein the hollow fiber membrane has an elongation at break of about 70% to about 210%.

8. The hollow fiber membrane according to claim 1 , wherein the hollow fiber membrane has a network structure.

9. A method of manufacturing a hollow fiber membrane, comprising:

preparing a spinning solution by using a composition comprising a polyvinylidene fluoride resin, a polyester plasticizer having a viscosity of about 100 cP to about 4,000 cP, a good solvent, and a non-crystalline polymer additive;

spinning the spinning solution to a wet-type coagulation bath to form a preliminary hollow fiber membrane;

extracting the plasticizer, the good solvent and the non-crystalline polymer additive from the preliminary hollow fiber membrane;

crystallizing the preliminary hollow fiber membrane; and

cold drawing the crystallized preliminary hollow fiber membrane.

10. The method according to claim 9 , wherein the non-crystalline polymer additive is a hydrophilic non-crystalline polymer additive and has a solubility parameter difference of about 5 MPa 0.5 or less with the polyvinylidene fluoride resin.

11. The method according to claim 9 , wherein the non-crystalline polymer additive is a hydrophobic non-crystalline polymer additive and has a solubility parameter difference of about 20 MPa 0.5 or less with the polyvinylidene fluoride resin.

12. The method according to claim 9 , wherein the wet-type coagulation bath has a temperature in the range of about 15° C. to about 40° C.

13. The method according to claim 9 , wherein crystallizing comprises heat treatment at a temperature of about 80° C. to about 150° C. for about 3 minutes to about 200 minutes.

14. The method according to claim 9 , wherein the composition comprises 100 parts by weight of the polyvinylidene fluoride resin, about 1.5 parts by weight to about 2.0 parts by weight of the polyester plasticizer, about 0.2 parts by weight to about 0.5 parts by weight of the good solvent, and about 0.01 parts by weight to about 0.2 parts by weight of the non-crystalline polymer additive.