Method for producing filter material formed of melt-blown non-woven mat sandwiching additional material

Claim 1

In a method for producing a melt-blown non-woven mat wherein a fiber-forming thermoplastic polymer resin is extruded in molten form through a row of individual nozzles each surrounded by an individual stream of hot gas which attenuates the molten resin into fibers that together form a fiber stream, and the fibers are collected on a receiver in the path of the fiber stream to form the non-woven mat, including the following steps providing at least two spaced rows of nozzles to produce first and second fiber streams spaced from each other, collecting the spaced fiber streams on the receiver to form a first non-woven mat portion and a second non-woven mat portion and with the first non-woven mat portion overlaying the second non-woven mat portion, injecting at a position intermediate the first and second fiber streams material different than the fiber-forming resin to have a substantial portion of the different material captured between the first and second fiber streams and thereby form a collected structure of the first and second mat portions sandwiching the substantial portion of the different material, providing the receiver as a substantially vertical surface and providing the spaced fiber streams as upper and lower substantially horizontal streams to be collected on the substantially vertical surface of the receiver, and wherein the injection of the substantial portion of the different material between the substantially horizontal fiber streams is provided by having the different material fall to the position intermediate the spaced fiber streams and wherein the fall of the different material is provided at a portion above both fiber streams to have the substantial portion of the different material pass through the upper fiber stream to the intermediate position.