Composite hollow fiber-type separation membranes, processes for the preparation thereof and their use

Abstract

A composite hollow fiber type separation membrane which has three layers comprising a selective separation layer, an ultra-microporous layer and a porous layer, said selective separation layer, said ultra-microporous layer, said porous layer being arranged in said order commencing from the inner surface of said hollow fiber membrane; wherein said selective separation layer is formed on said ultra-microporous layer without penetrating into said ultra-microporous layer and has a non-porous, dense structure, the average thickness of said layer being 0.01-2.mu., and the coefficient of variation in thickness thereof being less than or equal to 25%; wherein said ultra-microporous layer has a surface in which the presence of pores cannot be confirmed by 24,000 .times. scanning electron microscopy, but which has a fluid permeability at least 10 times that of said selective separation layer, the thickness of said layer being less than or equal to 0.08.mu.; and wherein said porous layer is a sponge structure comprising pores having a pore diameter of 0.1-1.mu. except for macro-voids and having a porosity of at least 50%, the thickness of said layer being 10-500.mu..

Dependencies are inferred from the claim text.