Patent GB-1391024-A (GB)
Title: Semi-permeable tubular assembly
IPC: B01D69/12
Filed: 1973-05-04
Abstract: 1391024 Fluid separation apparatus comprising semi-permeable membranes RHONEPOULENC SA 4 May 1973 [5 May 1972] 21327/73 Heading B1X A flexible tubular assembly for use in fluid separation apparatus, for example apparatus for reverse osmosis, ultrafiltration, pervaporation, or gas permeation, comprises a semipermeable membrane surrounding a cord which comprises a textile sheath surrounding a core composed of a plurality of longitudinally-extending yarns. The yarns, which may be single-strand or multi-strand filaments, may be twisted, stranded or braided, may be grouped in sheathed bundles, may be provided with transverse grooves and may be circular, elliptical or prismatic in cross-section; preferably the yarns have a circular crosssection and a diameter of between 0.1 and 3 mm. The textile sheath, which may be in the form of a filament wound helically around the yarns but preferably is a knitted, woven or braided sleeve, may consist of several superposed webs and may be circular, elliptical or prismatic in cross-section; preferably the sheath has a circular cross-section and an external diameter of between 1 and 8 mm. Specified materials from which the yarns may be made are glass, metals, metal alloys and artificial and synthetic textile materials; specified materials from which the textile sheath may be made are natural, artificial and synthetic textile materials such as polyamides, polyesters and polyolefins; the yarns and the sheath may be made of the same material. The assembly may be made by a process which comprises forming a core of at least two yarns, applying a textile sheath around the core thereby to form a cord, passing the cord through a tube heated to a temperature sufficient to soften the surface of the sheath thereby to smooth and adjust the diameter of the cord, impregnating the sheath with material effective to seal temporarily the interstices between the filaments of the sheath, casting the cord with a collodion solution, evaporating solvent of the solution from the coated cord thereby to form a semi-permeable membrane around the sheath, and at least partially removing the sealing material (which is inert to the sheath and immiscible with the collodion solution) from the resulting assembly. As exemplified, an assembly in the form of 52 single-filament polypropylene yarns surrounded by a woven textile polypropylene sheath surrounded by a cellulose acetate membrane having a thickness of 0.18 to 0.20 mm is formed by this procedure, using water as the temporary sealing material, and is sealed into the ends of a cylindrical chamber so that it lies along the longitudinal axis of the chamber; the resulting apparatus is used in the production of purified water from a feed which is applied to the exterior of the assembly and which is either a solution of sodium chloride or raw water containing calcium values. Reference is made to Specification 1056636 and French Patent 1506402 in respect of forming the membrane and to United States Patent 3446359 in respect of removing the temporary sealing material; reference also is made to Specifications 1054774 and 1325494.