Abstract: An electret filter formed by laminating a plurality of network electret film-split fiber fleeces having a different mesh size. It exhibits a high collecting efficiency with a very small pressure loss and without any appreciable fiber dropping, or any channeling.

Abstract: A flexible tubular filtering material possessing a braided cord structure wherein a number of yarns are intercrossed with each other in the right and the left directions and braided into a cylindrical form, or said material additionally with the fiber assembly layer installed around the cylindrical periphery of the filtering material, which is free of bending obstruction and shows little textural change in the outer and inner peripheries of the curved portion against bend formation, and which possesses high particle removal efficiency and long service life; and a flexible filter element comprising this filtering material in a flexible casing.They are useful for liquid filters, specifically as a fuel filter for automobiles.

Abstract: An electret sheet comprises a porous sheet made of a dielectric polymer and at least one solid material selected from the group consisting of organic materials, inorganic materials, and metallic materials, the porous sheet having the material spaced at various intervals and a method for the manufacture of the said electret sheet.

Abstract: An electret sheet comprises a porous sheet made of a dielectric polymer and at least one solid material selected from the group consisting of organic materials, inorganic materials, and metallic materials, the porous sheet having the material spaced at various intervals and a method for the manufacture of the said electret sheet.

Abstract: A filter for removing dust from fluids, which comprises fibers bonded each other with a binder and hot-pressed, having a fiber density of 0.01 to 0.1 at the fluid inlet side and a fiber density of 0.05 to 0.5 at the fluid outlet side with a continuous fiber density gradient and having a uniform distribution of fiber material in direction of thickness, and a process for the production thereof. The filter is particularly useful as an air filter for automobiles or air conditioners.

Abstract: A filter for removing dusts from fluids, which comprises fibers bonded each other with a binder and/or hot-pressed, having a fiber density of 0.01 to 0.1 at the side of inflow of fluid to be treated and a fiber density of 0.05 to 0.5 at the side of outflow of the fluid with a continuous fiber density gradient and having a uniform distribution of fiber material in direction of thickness, and a process for the production thereof. The filter is particularly useful as an air filter for automobiles or air conditioner.