Porous polytetrafluoroethylene tubings and process of producing them

Abstract

A porous polytetrafluoroethylene tubing, useful as artificial internal organs or industrial filtering materials for, for example reverse osmosis, ultrafilteration, etc., having a microporous fibrous structure in which the fibrous structure is composed of fibers and nodes connected with each other and the microporous fibrous structure differs between the outer surface portions of the tubing and the inner surface portions of the tubing, and a process for producing the porous resin tubing comprising heating a tubing made of an unsintered polytetrafluoroethylene under conditions in which the tube is stretched at least in the longitudinal direction of the tubing and such that the outer surface of the tubing is heated above about 327.degree. C and the inner surface of the tubing is heated to a temperature below the temperature of the outer surface.

Dependencies are inferred from the claim text.