Preparation of hollow fiber membranes for gas separation

Today, immersion precipitation is the most often used process for the preparation of gas separation membranes from polymeric materials. In this process a polymer solution in the form of a thin liquid film or hollow fiber is immersed in a nonsolvent bath where the polymer precipitates and forms a membrane. The immersion precipitation process can be performed by various means. The dual bath spinning process is one specific way which can be used, e.g., for the preparation of hollow fiber membranes for gas separation. In this process hollow fibers are spun by contacting the polymer solution with two properly chosen coagulents successively. The first coagulant is used to 'extract' solvent out of the polymer solution. The contact time is short in order to create a thin layer of high polymer concentration at the interface. The second coagulent is used to quickly precipitate the polymer solution to form the membrane. With this spinning process, hollow fibers with the intrinsic selectivity of the polymer material can be easily obtained without the necessity of coating. This thesis is aimed on extending the knowledge on membrane formation and on further developing the dual bath spinning process for the preparation of gas separation hollow fibers with both high selectivity and high flux.