| abstract |
In order to solve problems of damage due to fibrils or lint in a hollow fiber membrane having multifilaments that arise in the prior art, the present invention provides a further improved hollow fiber membrane in which an open-type tubular knitwork using monofilaments is spirally manufactured and the resultant knitwork is embedded into a polymer resin. The open-type tubular knitwork is characterized in that it is weaved at a fixed angle by each monofilament so as to form either a rhomboid or a diamond shape. The monofilaments are weaved onto a plasticized cable to form the knitwork, and a polymer dope for the hollow fiber membrane is coated on the knitwork, such that the knitwork is embedded into the polymer, and then the dope is coagulated. Here, the plasticized cable determines the inner diameter of the hollow fiber membrane. The hollow fiber membrane, in which the open-type knitwork is embedded as described above, is expandable (extendable) in a longitudinal direction and is expandable in a radial direction, thereby enabling biaxial expansion. That is, the hollow fiber membrane is flexible in the radial direction as well as in the longitudinal direction. Due to the flexibility in the radial direction, the hollow fiber membrane can be backwashed at a higher pressure than can a hollow fiber membrane made using multifilaments, which is hardly expandable in the radial direction. Thus, manufacturing efficiency is improved. |