Filter for aqueous solutions or dispersions - made by rendering hydrophobic thermoplastic film hydrophilic with surface active agent

摘要

A filter membrane of thermoplastic film is used for filtering aqs. solns. and dispersions. It is produced by rendering hydrophilic, a finely porous hydrophobic polymer film using surface-active agents. The filter is cheap to produce. The filter comprises middle layer of 400 mu polypropylene mat, two intermediate layers of 25 mu perforated biaxially stretched polypropylene film which is sealed both sides, and two outer layers of 25 mu finely porous polypropylene film. This filtration structure is immersed in a satd. aq. soln. of sodium lauryl thiosulphate at room temp. washed with water, dipped in 0.5% aq. potassium permanganate soln. washed and dried. The outer layers are thus rendered hydrophilic.