Hollow-fibre membrane having novel structure, and production method therefor
The present invention relates to a hollow-fibre membrane having a novel structure and to a production method therefor. The hollow-fibre separation membrane of the present invention has an outermost shell surface pore size of between 0.001 and 0.05 μm and a mean pore size of between 0.01 and 0.1 μm while having, in sequence from the outermost shell surface, a dense sponge structure, a finger-like sponge structure and a mixed sponge-bead structure; and, because of this specific triple structure, the invention has outstanding mechanical strength, porosity and water permeability alike while also having a high performance whereby it is possible to eliminate even viruses.
1. A hollow fiber membrane in which (i) a dense sponge structure having pores with a size of 0.001 to 0.05 μm, (ii) a finger-like sponge structure, and (iii) a sponge-bead mixed structure are formed in the order numbered from the outermost surface of the membrane.
2. The hollow fiber membrane of claim 1 , wherein the pores formed on the outermost surface have a size of 0.001 to 0.01 μm.
3. The hollow fiber membrane of claim 1 , wherein the dense sponge structure has a thickness of 0.01 to 20 μm, the finger-like sponge structure has a thickness of 10 to 100 μm, and the sponge-bead mixed structure has a thickness of 50 to 200 μm.
4. The hollow fiber membrane of claim 1 , wherein the density of the beads contained in the sponge-bead mixed structure (iii) is gradually reduced from the central part to the internal coagulant-contacting part of a membrane.
5. The hollow fiber membrane of claim 1 , wherein the hollow fiber membrane is polyvinylidene fluoride (PVDF)-based membrane.
6. The hollow fiber membrane of claim 1 , wherein the membrane has an ability to remove viruses.
7. A method of preparing the hollow fiber membrane of claim 1 as a continuous process, the method comprising:
(i) supplying a polyvinylidene fluoride (PVDF)-based resin to an extruder;
(ii) supplying a good solvent and a poor solvent to the extruder;
(iii) mixing the supplied materials by using a screw in a cylinder of the extruder; and
(iv) extruding and spinning out the mixed solution.
8. The method of claim 7 , wherein the supplied materials are mixed and molten by screw rotation at a cylinder temperature in step (iii).
9. The method of claim 8 , wherein the temperature of the cylinder is adjusted to 50 to 250° C.
10. The method of claim 8 , wherein the rotation speed of the screw is adjusted to 150 to 300 rpm.
11. The method of claim 7 , wherein the mixed solution in step (iv) is spun out with an internal coagulant.
12. The method of claim 7 , further comprising cooling and solidifying the solution spun out from (iv) using a coagulation bath.