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Abstract

Covers an immersible molecular filter unit having a body that is formed from a porous polymeric material of generally cylindrical shape, preferably rounded at least at one of its ends. A tubular connector is mounted at one end of this body, with a bore that communicates with the porous network of the body. An anisotropic membrane encapsulates the body and is formed with an integral collar portion that engages about a portion of the connector, where it projects from the body, in substantially fluid-tight fashion. Preferably the membrane, which is formed in situ, is shrunk about the tube and the body, and is solvent welded to the connector. This unit is formed by dipping the body and the juxtaposed connector in a polymer casting solution, to encapsulate the porous body and a part of the connector. The dip-coating unit is then converted to an anisotropic membrane. The preferred way to do this is immersion in a liquid that is not a solvent for the cast polymer, but that is miscible with the solvent of the casting solution, to cause formation of a highly anisotropic structure. Preferably, this is accompanied by simultaneous shrinking of the applied coating and solvent welding of the collar portion of the coating to the tube. The viscosity of the casting solution and the porosity of the body are such that there is substantially no penetration of the casting solution into the porous structure of the body.

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