Spinneret block with unitary spinneret body and nozzles for use in the manufacturing of spun-blown fibers

Abstract

The present invention relates to a particular execution for a die block for spun-blowing process for forming a fibers or filaments that may further form a spun-blown web or nonwoven comprising such a formed fibrous web, e.g. as a layer in a multi-layer composite web. The die block comprises a spinneret block with unitary spinneret body and nozzles.

1 . A die block for forming meltblown filaments comprising:
 wherein said spinneret block, said air distribution plate, said exterior air plate, and said cover strip mounted in this order and secured by said securing means such that
 said nozzles protrude through corresponding openings in said air distribution plate and further through corresponding openings in said exterior air plate, and 
 such that polymer passageways are formed for molten polymer passing from said polymer supply side of said spinneret body through said nozzles; and 
 such that air passageways are formed for air passing from said air supply through openings in said air distribution plate and said exterior air plate; 
   whereby said openings in said exterior plate and said nozzles are adapted so as to allow molten polymer exiting said nozzles and air flowing through the openings of said exterior air plate are essentially parallel,   wherein   said spinneret body and said nozzles are unitary.   
     
     
         2 . A die block according to  claim 1 , satisfying one or more of the conditions selected from the group consisting of
 the inner diameter of the nozzle being less than about 1.25 mm;   the outer diameter of the nozzle being less than about 2 mm;   the nozzle exhibiting a length of less than about 50 mm;   the nozzle exhibiting a length of more than about 10 mm;   the nozzle exhibiting a L/d ratio of less than about 50;   the die block exhibiting a CD width of more than 250 mm.   
     
     
         3 . A die block according to  claim 1 , further comprising pre-holes in said block, said pre-holes
 extending from the upper surface positioned towards the supply of the molten polymer towards said capillaries   in the form of countersinks to the capillaries of said nozzles.   
     
     
         4 . A die block according to  claim 1 , wherein the transition of said nozzles to the base of said block exhibits a radius of more than about 0.1 mm. 
     
     
         5 . A die block according to  claim 1 , wherein said array of nozzles comprises at least two sub-arrays comprising nozzles differing from nozzles of a different sub-array in at least one of the dimensions selected from the group consisting of
 inner diameter of the nozzle;   outer diameter of the nozzle,   length of the nozzle.   
     
     
         6 . A die block according to any of the preceding  claim 1 , wherein further
 said array of nozzles comprises at least two sub-arrays, each of said sub-arrays being connected to a separate polymer supply system adapted to supply molten polymer to said sub-array differing in at least one of the features selected from the group consisting of
 polymer type; 
 polymer flow rate; 
 polymer pressure; 
 polymer temperature. 
   
     
     
         7 . (canceled) 
     
     
         8 . A method for the manufacture of a die block comprising a spinneret block comprising a spinneret body and a plurality of nozzles, an air distribution plate, and an exterior air plate, comprising:
 providing a single piece of die block precursor;   machining from said single piece of die block precursor
 a spinneret block comprising
 nozzles; 
 
 air inlet and distribution chamber; 
 an air distribution plate; 
 an exterior air plate, 
   wherein said machining is high precision CNC treatment.   
     
     
         9 . (canceled) 
     
     
         10 . Process for forming a nonwoven web comprising meltblown fibers, comprising the steps of
 providing equipment according to  claim 1 ,   providing a thermoplastic polymer for forming MB fibers, exhibiting a MFI from 30 to 2000,   forming filaments by applying a pressure of less than 70 bar.   
     
     
         11 . A die block according to  claim 3  comprising pre-holes in said block, wherein said pre-holes exhibit a chamfering angle of between 30° and 60°. 
     
     
         12 . A die block according to  claim 3  comprising pre-holes in said block, wherein said pre-holes exhibit a diameter of between 1.5 to 4 times the inner diameter of said capillaries. 
     
     
         13 . A die block according to  claim 3  comprising pre-holes in said block, wherein said pre-holes exhibit a length of more than about 2 mm. 
     
     
         14 . A die block according to  claim 3  comprising pre-holes in said block, wherein said pre-holes exhibit a length of less than about 20 mm. 
     
     
         15 . A die block according to  claim 3  comprising pre-holes in said block, wherein said pre-holes exhibit a length of less than about 14 mm. 
     
     
         16 . A die block according to  claim 3  comprising pre-holes in said block, wherein said pre-holes exhibit a length of less than about 8 mm. 
     
     
         17 . A process for forming a nonwoven web according to  claim 10 , wherein the operation of forming filaments is executed at a pressure of less than 50 bar at the polymer supply. 
     
     
         18 . A process for forming a nonwoven web according to  claim 17  wherein the operation of forming filaments is executed at a pressure of less than 45 bar at the polymer supply.