Fabrication of a fluoropolymer hollow fiber having a defect-free separation layer
AssigneeHoechst Celanese Corporation
InventorsTai-Shung Chung, Edward R. Kafchinski, Michael Haubs
Life of this patent
Estimating the term…
Abstract
Asymmetric fluoropolymer hollow fibers having a thin, dense, inner separation layer that is essentially defect-free. In the process of this invention, a fluoropolymer dope is spun into a hollow fiber using a hollow fiber die, a core solvent, preferably comprising water, and a coagulation bath, preferably comprising a water-acetone mixture. Due to solubility and surface tension differences, the outer layer of the fiber does not coagulate quickly enough to form a dense layer, and remains porous, but the core solvent causes the inner surface of the hollow fiber to coagulate into a thin, dense, defect-free layer.
Claims3
An asymmetric hollow fiber for fluid separation having an outer surface and an inner surface, said fiber comprising a fluoropolymer having a solubility at 25.degree. C. in acetone that is no greater than about 20 percent, wherein said inner surface is a dense, essentially defect-free layer and said outer surface is porous, and further wherein said fiber has a separation factor of at least about 4 for oxygen and nitrogen;
- said fiber made by spinning a dope comprising said fluoropolymer and a solvent from a hollow fiber die using water as a hollow fiber core solvent, and immersing said fiber in coagulation bath comprising a water-acetone mixture, wherein said fiber does not pass through an air gap between said die and said bath.
Dependencies are inferred from the claim text.