Patent ID: 6521025
Filing Date: 2003-02-18
Classification: B01D,Y10S

Abstract:
A method of producing a hollow fibre membrane suitable for use in gas separation, the method comprising the steps of:a) providing a shear-thinning dope composition having a power law index of less than 1 and greater than about 0.2; b) providing a bore coagulant in the form of an aqueous salt solution with a water activity in the range 0.80 to 0.95; c) extruding the dope composition through an annulus of a spinneret at a rate which induces levels of shear in the dope composition at the wall regions of the annulus sufficient to longitudinally align the polymer molecules in the active layer of the resultant nascent hollow fibre membrane, said levels of shear being in excess of 4200 s-1; and d) introducing the nascent hollow fibre membrane to a closely-coupled convection chamber supplied with a controlled influx of gas for dry phase separation by forced convection to produce at the exterior surface of the membrane a thin, dense active layer in which the aligned polymer molecules are fixed in position, thereby defining a plurality of regularly spaced and essentially uniformly-sized free volume cavities which allows gases to be separated with a high degree of selectivity.