| 摘要 |
PURPOSE:To facilitate washing of a hollow yarn membrane for restoring filtration capacity without removing the membrane from a purification device by building-in a hollow yarn membrane comprising a hydophobic material contg. fine pores having high bubble point being made hydrophilic and fine pores having low bubble point being made hydrophobic, in a filter module. CONSTITUTION:Hydrophobic hollow yarns of polyethylene, etc. contg. fine pores having different degree of bubbles point are made hydrophilic by treating in a hydrophilizing solvent such as ethanol, then the pores having low bubble point are made hydrophobic by blowing gas. When the solvent in the module which has been made hydrophobic is replaced with a solvent such as water, the water can not intrude into the pores having low bubble point because such pores are made hydrophobic. Thus, a module having superior fractionating characteristic is obtd. When a gas held at a certain pressure is introduced into the hollow yarn in the backwashing stage, the gas is blown out of the fine hydrophobic pores alone to realize backwashing effect. The hydrophilic fine pores retain the hydrophilicity. Therefore, the filtration capacity is not deteriorated even after backwashing. |
