METHODS FOR PREPARING ANISOTROPIC MEMBRANES AND MEMBRANES PREPARED THEREFROM

07-0433 METHODS FOR PREPARING ANISOTROPIC MEMBRANES AND MEMBRANES PRODUCED THEREFROM ABSTRACT OF THE DISCLOSURE Anisotropic membranes are prepared from a solution of a membrane-forming polymer in a liquid carrier. The polymer solution is provided in the form of a precursor and is then coagulated in a liquid coagulant comprising water to form the anisotropic membrane. The liquid carrier used in the methods comprises an N-acylated heterocyclic solvent which can be represented by the structure: wherein X is -CH2-, -N(R')- or -O-; R is hydrogen, methyl or ethyl; and R' is hydrogen or methyl. The methods are particularly useful for preparing anisotropic hollow fiber membranes. In forming anisotropic hollow fiber membranes, the solution of hollow fiber-forming polymer in the liquid carrier is extruded through an annular spinnerette to form a hollow fiber precursor, and the hollow fiber precursor is coagulated in a liquid coagulant comprising water to form the hollow fiber membrane, The methods are attractive for producing polysulfone hollow fiber membranes which have a homogeneously-formed, thin selective skin on an open cellular support and which exhibit high resistance to collapse. The membranes are especially useful for the separation of gases,