Varying density cartridge filters

Abstract

Abstract Polypropylene or other fiber-forming polymer is melt extruded as a continuous molten stream which is attenuated by a plurality of gaseous streams into a fine filament and projected onto a rotating collection surface, such as a mandrel. During collection there is changed, one or more times, at least one of (i) temperature of the filament-forming material, (ii) the speed of extrusion, (iii) the speed of rotation of said collector, (iv) the distance between extruder and collector, or (v) the weight of an idler roll on the collector, thereby to form an annular layer whose density differs relatively from the layer immediately preceding it. The resulting cylindrical, self-bonded, nonwoven structure has a predetermined, density profile. For uses such as filtration, the fluid to be filtered enters from the low density side so that solids will deposit throughout the filter more or less uniformly rather than building up so much in the first-contacted layer that it becomes fully clogged before the balance has had any appreciable solids build-up.

Inventors

• 👤 C Vogt
• 👤 J Soehngen
• 👤 J Polise

Bibliographic Details