Patent ID: 8017066
Filing Date: 2011-09-13
Classification: B29C,D01D,D04H

Abstract:
1. A method for forming a spun bond nonwoven web from extruded polymer filaments in a machine having a machine width, comprising the steps of: (a) extruding a plurality of continuous thermoplastic polymeric filaments through a spinneret; (b) non-eductively drawing and cooling a curtain of said filaments in a pressurized quench chamber having an ingress opening at the top of the machine extending substantially across the machine width, said curtain of filaments having a substantially constant filament distribution across the machine width, said step of non-eductively drawing and cooling including dimensioning and configuring the quench chamber to avoid substantial contact between said filaments and interior surfaces of the quench chamber, and providing a quench chamber volume sufficient to allow solidification of said filaments within said quench chamber; (c) supplying the pressurized quench chamber with compressed quench fluid at a temperature lower than the temperature of the filaments in the quench chamber and at a pressure in a range from about 0.1 to 4 bar; (d) introducing said quench fluid on at least one side of said curtain of filaments and directing said fluid into contact with said curtain of filaments in said quench chamber to cause cooling of the filaments; (e) creating a turbulent mix of fibers and quench fluid in an impingement zone located adjacent the bottom of said quench chamber with sufficient turbulence to produce efficient energy transfer from quench fluid velocity to fiber velocity; (f) increasing the turbulence of said mix in said impingement zone by providing lower surfaces of the chamber tapering toward each other in the direction of filament flow through the chamber and terminating at facing edges of respective knife structures at said impingement zone; (g) flowing the turbulent mix of fibers and quench fluid as a stream to a lower pressure environment through a drawing slot in the form of a chamber exit nozzle defined by and between the facing edges of said knife structures and extending substantially across the machine width at the bottom of said chamber and at the impingement zone such that the drawing slot has no substantial nozzle length in the direction of flow through the nozzle to thereby minimize collection of dirt and polymer and monomer in the exit nozzle, whereby, within the first few inches after passing through the drawing slot the turbulent mix stream is rapidly slowed as velocity energy of the quench fluid is transferred to the fibers and the stream entrains air from the lower pressure environment and expands; and (h) collecting the slowed filaments for formation into a non-woven fabric sheet on a web forming conveyor.