Molded fibrous filtration products

A molded filtration product which exhibits a pressure drop of no more than about 30 millimeters of water at a face velocity of 85 liters per minute, comprising at least three fibrous layers which have been subjected to heat and molding pressure while assembled in layer-to-layer contact with one another, two of the layers being shaping layers that are disposed on each side of another fibrous layer that serves as a filtration layer, (b) in total have a basis weight between about 40 and 150 pounds per ream, (c) in total contribute no more than about 20 percent of the pressure drop through the finished filtration product, and (d) comprise bicomponent fibers bound together at points of fiber intersection by coalescence of binder material carried as one component on the fibers, the shaping layer upstream of the filtration layer having a basis weight of no greater than about 50 pounds per ream;

• the filtration layer removing particulates from a gaseous stream passed through the filtration product in a higher percentage than the shaping layers remove them, and the filtration layer being attached to the shaping layers by at least fiber entanglement, and being conformed into contact with the shaping layers over the full interface between the layers.

A method for preparing a molded filtration product comprising

• (a) assembling in face-to-face contact at least two fibrous layers, one or more of the layers being a shaping layer that (a) in total have a basis weight no greater than 150 pounds per ream, (b) in total have a loft of at least 5 millimeters, and (c) at least one of which comprise fibers that can be bound together at points of fiber intersection by coalescence of binder material on the fibers, and another of the layers being a fibrous filtration layer which removes particulates from a gaseous stream passed through the filtration product in a higher percentage than the shaping layer removes them;
• and
• (b) subjecting the assembly to heat and pressure sufficient to mold the assembly to a non-flat shape whereupon a molded filtration product is formed in which the fibers of at least one of the shaping layers are bonded together by coalescence of binder material on the fibers, the shaping layers in total contribute no more than 20 percent of the pressure drop through the finished filtration product, and the filtration layer is attached to the shaping layer or layers by at least fiber entanglement, and is conformed into contact with the shaping layer or layers over the full interface between the layers.