| 摘要 |
PURPOSE:To prepare a hollow yarn membrane with treating capability not to be lowered even in the external pressure method by providing as the outer surface only as the skin layer and constituting the outer surface with a porous layer having an opening ratio and pore diameters of a specific value or more. CONSTITUTION:For instance, ultrafiltration membranes constituted of polyether imide and having skin layers on both outer and inner surfaces are wet prepared and air-dried to prepare dry hollow yarn filter membranes, which are bundled, bonded and fixed with casting resin, to prepare as a filter element. Ethylene glycol is applied on both ends of said filter element, and then glycerin is applied over all the membrane to protect the skin layer on the outer surface. One end of the filter element 7 is connected with a vacuum vessel 4, while the other end is connected with the vessels 5 and 6 for water and treating solution such as dioxane or the like. Cocks 1 and 2 are opened to make the pressure of the inside of the membrane lower than that on the outside, and the treating solution is introduced to melt or decompose the membrane and remove the inner surface of the skin layer. The cock 1 is closed and, after a given period of time, the cock 2 is closed and cocks 1 and 3 are opened to wash the inside of the membrane with water.
|
