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Abstract

A porous polypropylene hollow fiber membrane is disclosed which is characterized by the fact that the solid phase in the inner surface region thereof is formed with particles of polypropylene closely fused and joined to give rise to a continuous phase while partially exposed through the surface thereof, the solid phase in the interior and the outer surface region thereof is formed with particles of polypropylene interconnected in the direction of axis of fiber to give rise to a multiplicity of lumps of polypropylene, and the interstices between these solid phases has continuous pores interconnected in the form of a three-dimensional network. When this porous polypropylene hollow fiber membrane is used in an artificial lung, without reference to the choice between the type adapted to pass blood inside the hollow fiber membrane, it exhibits a high gas-exchange capacity without infliction of injury upon blood cells, aggravation of pressure loss, or leakage of blood plasma. Further a flat-film type porous polypropylene membrane possessing a microreticular structure is disclosed which is characterized by the fact that either or both of the opposite surface region of the porous membrane forms a surface layer possessing practically the same micro-reticular structure as in the interior of said membrane and said membrane possesses an average pore diameter in the range of 0.1 to 5.0 .mu.m, a bubble point of not more than 2.0 kgf/cm.sup.2, a porosity in the range of 60 to 85%, a water permeability of not less than 100 ml/min.mmHg.m.sup.2 and a wall thickness in the range of 30 to 300 .mu.m. When this flat-film type porous polypropylene membrane is used for blood plasma separation, it effects the blood plasma separated at a high speed and sparingly entails occlusion of blood cells or hemolysis.

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