| 摘要 |
PROBLEM TO BE SOLVED: To remove metals such as alkali metals and heavy metals from a novolac polymer by passing an organic solvent solution of the polymer through a filter medium on which a zeta potential acts. SOLUTION: The filter medium on which a zeta potential acts is exemplified by a functional filter medium prepared by adding a cationic-charge modifier desirably being a polyamidepolyamine epichlorohydrin cationic resin to a filter medium such as cotton, cellulose, a polyester, active carbon, or zeolite. It is desirable that the thickness of the functional filter medium is 0.01-10 cm and that diameter of the pores of the medium or of the openings formed among particles of the medium is 0.1-1.0 μm. It is desirable to use the filter medium in combination with an ion exchanger and/or a chelate former. That is to say, the functional medium can adsorb charged particles present in the solution to thereby catch metallic impurities smaller than the pore of the medium by the help of the potential difference generated when the polymer solution is passed therethrough, while the ion exchanger and/or the chelate former can trap free ions in the solution. |
