Process for making a filter having a continuous density gradient

摘要

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.