Method of making a filter element

摘要

A homogeneous mixture of a base and a binder material or fiber that is compressed to form a mat or sheet of selected porosity. The binder material has at least a surface with a melting temperature lower than that of the base fiber. The sheet is formed into a selected geometric shape and thermally fused to bind the base fiber into a porous filter element. The preferred shape is a helically wound tube of plural sheets, each sheet being self-overlapped and compressed to overlap another sheet. Each sheet preferably heated and compressed individually and the sheets may be selected to have different porosities and densities. The binder fiber is selected from the group consisting of thermoplastic and resin, and the base fiber is selected from the group consisting of thermoplastic and natural.