Abstract: Processes are disclosed for coating the exteriors of a plurality of hollow fibers which are suitable for fluid separations and which are assembled in the form of a bundle. The processes involve immersing the bundle of hollow fibers in a coating liquid containing material suitable for forming the coating and a substantial amount of solvent. A pressure drop from the exteriors to the interiors of the hollow fibers is provided to result in the formation of a deposit on the exteriors of the hollow fibers. The processes of this invention enable essentially the entire exterior surfaces of the hollow fibers to be coated without undue sticking of the hollow fibers or providing undesirably thick coatings on the hollow fibers in any portion of the bundle or on a portion of any of the hollow fibers.

Abstract: Hollow filaments, which are suitable for use in separating one or more components from a fluid mixture by selective permeation, are embedded, or potted, in a solid potting mass and the potting mass is severed to expose fluid communication openings of the hollow filaments. In accordance with the invention a thin layer of the solid potting mass having the hollow filaments embedded therein is removed by planing or milling using a knife blade edge moving in an essentially arcuate path at sufficient velocity to cause fracturing of at least one of the hollow filaments and solid potting mass at the point of contact with the knife edge.