Abstract: A composite filtration medium web of fibers containing a controlled dispersion of a mixture of sub-micron and greater than sub-micron diameter polymeric fibers is described. The filtration medium is made by a two dimensional array of cells, each of which produces a single high velocity two-phase solids-gas jet of discontinuous fibers entrained in air. The cells are arranged so that the individual jets are induced to collide in flight with neighboring jets in their region of fiber formation, to cause the individual nascent fibers of adjacent jets to deform and become entangled with and partially wrap around each other at high velocity and in a localized fine scale manner before they have had an opportunity to cool to a relatively rigid state. The cells are individually adjusted to control the mean diameters, lengths and trajectories of the fibers they produce.

Abstract: A composite filtration medium web of fibers containing a controlled dispersion of a mixture of sub-micron and greater than sub-micron diameter polymeric fibers is described. The filtration medium is made by a two dimensional array of cells, each of which produces a single high velocity two-phase solids-gas jet of discontinuous fibers entrained in air. The cells are arranged so that the individual jets are induced to collide in flight with neighboring jets in their region of fiber formation, to cause the individual nascent fibers of adjacent jets to deform and become entangled with and partially wrap around each other at high velocity and in a localized fine scale manner before they have had an opportunity to cool to a relatively rigid state. The cells are individually adjusted to control the mean diameters, lengths and trajectories of the fibers they produce.