PURPOSE: To wash-out liquid paraffin without deteriorating membrane function by washing the inside surface of a hollow fiber obtained by using the liquid paraffin as a core solution with a specific aliphatic ether followed by a glycerin treatment.
CONSTITUTION: The inside surface of a hollow fiber obtained by using liquid paraffin as a core solution is washed out with an aliphatic ether of formula (R1-R3 are independently H or methyl and at least one of R1 and R2 is methyl). Because the aliphatic ether extracts the glycerin impregnated in the hollow fiber for the purpose of humectation, the washed hollow fiber is subjected to glycerin treatment with a glycerin-containing solution having a boiling point of 30-150°C followed by the removal of a solvent (e.g. isopropanol) of the glycerin solution by drying before the hollow fiber is put to practical use.
MATSUDA HIROO
OMORI SATOSHI
