Membrane filter tube and method of preparation

A membrane filter which comprises:

• (a) a cylindrical prefilter tube for the filtration of gases and having an exterior and an interior surface and one and an other end and of a defined edge thickness at the one and other end, the filter tube comprising a plurality of nonwoven, randomly disposed, borosilicate glass fibers having a diameter of about 0.01 to 10 microns, the borosilicate glass fibers bonded together with fluorocarbon bonding agent to form a self-supporting, end axially-compressible, self-gasketing filter tube of defined filter capacity and efficiency;
• and
• (b) a heat-shrunken fluorocarbon, microporous membrane bonded by a thermoplastic polymer into a close fitting, snug, secure relationship about the exterior surface of the filter tube and across the full edge width of the filter tube at each end of the filter tube and extending slightly within and against the interior surface of the filter tube at each end to provide a membrane filter subject to sealing against a housing surface by end axial compression across the full edge width of the microporous membrane.

A method of preparing a microporous membrane filter to be sealed within a filter tube housing by axial compression of the end of the membrane filter and which method comprises:

• (a) securing a polymeric microporous membrane material to the external cylindrical surface of an end axially compressible, self-gasketing, porous prefilter tube and which filter tube has a one and an other end and a defined thickness;
• and
• (b) overlapping and securing the ends of said microporous membrane across the full edge width of the one and other ends of the filter tube.