Fibrous webs of bi-component melt-blown fibers of thermoplastic polymers from a bi-component spinnerette assembly of multiple rows of spinning orifices

Abstract

Fibrous webs of bi-component fibers are made by extruding a polymer through one set of nozzles arranged in multiple rows, and another polymer through a second set of nozzles each of which surround a nozzle of the first set. In the design of having a nozzle inside a nozzle, contact between polymer pairs can be avoided inside a spinnerette, and bic-omponent fibers of unique properties can be produced. Polymer pairs can be grouped together which could not be co-extruded in traditional designs where laminar flow of layered molten masses of different polymers is rerquired.

What is claimed is:  
     
         1 . A fibrous web comprising a coherent entangled mass of melt-blown bi-component fibers, said fibers individually comprise a first polymeric material extending longitudinally along the fiber through a first circular portion of the cross-sectional area of said fibers and a second polymeric material adhered to said first polymeric material and extending logitudinally along said fiber through a second cylindrical portion of the cross-sectional area of the fiber surrounding said first circular portion of the cross-sectional area of the fiber, said fibers being prepared by 
 (a) extruding a mass of said first polymeric material through a first set of nozzles arranged in multiple rows and being fed from a first polymer feed chamber, and a mass of said second polymeric material being fed through a second set of nozzles arranged in multiple rows and being fed from a second polymer feed chamber, said second set of nozzles surrounding each of said first nozzles thus forming nozzle pairs, and said second nozzles having a larger inside diameter than the outside diameter of said first nozzles to form a bi-component extrudate    (b) advancing said extrudate into high velocity gas streams surrounding circumferencially each individual nozzle pair of said first and second set of nozzles and    (c) attenuating said bi-component extrudate from each of said nozzle pairs to form said bi-component fibers,    (d) said fibers being collected on a moving screen to form said fibrous web.    
     
     
         2 . A fibrous web as of  claim 1  wherein said fibers being prepared by 
 (a) extruding a mass of said first polymeric material through said first set of nozzles arranged in multiple rows, and a mass of said second polymeric material through said second set of nozzles arranged in multiple rows,  
 (b) whereby said first set of nozzles is recessed into said second set of nozzles by at least 0.030″.  
 
     
     
         3 . A fibrous web as of  claim 1  wherein said fibers being prepared by 
 (a) extruding a mass of said first polymeric material through said first set of nozzles arranged in multiple rows, and a mass of said second polymeric material through said second set of nozzles arranged in multiple rows,  
 (b) whereby the ends of said first set of nozzles are shaped into a semi-circle fitting into said second set of nozzles thus shaping a fiber having a cross-section in which each of said first and second polymeric materials occupy approximately a side-by-side semi-circle.  
 
     
     
         4 . A fibrous web of  claim 1  where the points of fiber intersection are bonded by coalescence of polymeric material.