Spinneret block with readily exchangable 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 spun-blown web, e.g. as a layer in a multi-layer 5 composite web. The die block comprises nozzles that are readily removable, and preferably chamfered.

1 . A die block for forming spun-blown filaments comprising
 molten polymer supply;   air supply;   a spinneret block comprising
 an upper plate comprising a polymer supply side, and 
 a lower plate, and 
 a plurality of nozzles; 
   an air distribution plate comprising openings;   an exterior air plate comprising openings;   a cover strip   securing means,   
       wherein said spinneret block, said air distribution plate, said exterior air plate, and said cover strip are 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 upper plate 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 at an angle of less than 30°, 
       wherein
 said spinneret block comprises
 an upper plate positioned towards the molten polymer supply, comprising
 a polymer supply cavity 
 and upper plate openings exhibiting at least at their lower end an upper 
 plate opening diameter; 
 a lower plate positioned away from said molten polymer supply, comprising lower plate through holes concentric to said upper plate through holes exhibiting 
 an upper portion positioned towards said upper plate with an upper portion diameter, and an upper portion length 
 and a lower portion positioned opposite of said upper portion with a lower portion diameter and a lower portion length, whereby said upper portion diameter is larger than said lower portion diameter, 
 
 
 said nozzles comprising
 an upper section exhibiting an upper section outer diameter 
 and a lower section exhibiting a lower section outer diameter; 
 a capillary as an inner through hole through said nozzle; 
 
 
       and wherein
 said upper sections of said nozzles fit removably into the upper portions of said lower plate, 
 
       wherein further
 said upper plate opening diameter and said lower plate opening diameter or said chamfering exhibit a difference of less than 50 μm. 
 
     
     
         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 nozzle is executed with a pre-hole exhibiting a diameter of more than about 0.5 mm;   the nozzle is executed with a pre-hole exhibiting a pre-hole diameter of less than about 4 mm;   the nozzle exhibits transition zones between the sections of differing diameters which extend more than 2 mm;   the nozzle exhibits transition zones between the sections of differing diameters which extend less than 2 mm;   the nozzle is executed with a pre-hole exhibiting a length of more than 2 mm, whereby this length includes the length of a transition zone towards a larger diameter;   the nozzle is executed with a pre-hole exhibiting a length of more than 2 mm, whereby this length includes the length of a transition zone towards a larger diameter;   the nozzle is executed with a pre-hole exhibiting a length of less than about 20 mm, whereby this length includes the length of a transition zone towards a larger diameter;   the die block exhibiting a CD width of more than 250 mm.   
     
     
         3 . A die block according to  claim 1 , wherein said openings in said upper plate satisfy one or more of the conditions selected from the group consisting of
 comprising a chamfering at a chamfering angle of between 30° and 60° or with a rounded profile,   exhibiting a chamfering diameter of between 1.5 to 4 times the inner diameter of said capillaries,   exhibiting a length of more than about 2 mm,   exhibiting a length of less than about 20 mm;   exhibiting a length of less than 8 mm;   tapering from said polymer supply side towards the opposite side.   
     
     
         4 . A die block according to  claim 1 , wherein said nozzles form an array, further comprising stationary pins, said stationary pins being positioned at the periphery of said array. 
     
     
         5 . A die block according to  claim 1 , wherein
 said upper plate further comprises
 at least one row groove
 positioned on the side towards said first plate and 
 oriented parallel to said row of nozzles, 
 
 and optionally a circumferential groove circumscribing said nozzle row or said array of nozzles, respectively, 
   wherein
 at least one row of nozzle holes is positioned in a row groove, thereby forming said chamfering section of said nozzles, and 
 said groove is adapted to receive a sealant. 
   
     
     
         6 . A die block according to  claim 5 , wherein said sealant compound is adapted to prevent in an assembled state of said die block the flow of the molten polymer
 into nozzle holes which are positioned in said row groove(s),   along the gap between said first and said second plate of said die body towards neighbouring row grooves, or nozzle holes, or the outside.   
     
     
         7 . A die block according to  claim 5 , wherein said grooves exhibits a rounded cross-sectional shape or a rounded base. 
     
     
         8 . A die block according to  claim 5 , wherein said grooves exhibit one or more of the dimensions selected from the group consisting of
 a width of more than about 1 mm,   a width of less than about 10 mm,   a depth of more than about 1 mm,   a depth of less than about 10 mm.   
     
     
         9 . A die block according to  claim 5 , wherein said row groove comprises a sealant, preferably selected from the group consisting of acrylic resins, adhesive sealants, butyl rubber, elastic sealants, epoxy thermosets, latex sealants, plastic sealants, polysulfide sealants, polyurethane sealants, rubber sealants, silicone sealants, preferably polysiloxanes, or urethane sealants, or fluorocarbon polymers, or more preferably of the silicon or PTFE type. 
     
     
         10 . 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.   
     
     
         11 . A die block according to  claim 1 , wherein 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.   
     
     
         12 . Process for forming a nonwoven web comprising melt-blown fibers, comprising the steps of
 providing equipment according to  claim 1 ,   providing a thermoplastic polymer for forming melt-blown fibers, exhibiting a MFI from 30 to 2000 for 10 minutes at 2.16 kg at appropriate material class temperature, and   forming filaments by applying a pressure of less than 70 bar.   
     
     
         13 . A die block according to  claim 1 , 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 at an angle of less than about 10°. 
     
     
         14 . A die block according to  claim 4 , wherein said stationary pins exhibit the same outer diameters and lengths as a nozzle, 
     
     
         15 . A die block according to  claim 5 , wherein said upper plate further comprises
 a circumferential groove circumscribing said nozzle row or said array of nozzles, respectively.   
     
     
         16 . A die block according to  claim 9 , wherein said sealant is selected from the group consisting of acrylic resins, adhesive sealants, butyl rubber, elastic sealants, epoxy thermosets, latex sealants, plastic sealants, polysulfide sealants, polyurethane sealants, rubber sealants, silicone sealants. 
     
     
         17 . A die block according to  claims 15 , wherein said sealant is selected from the group consisting of polysiloxanes, urethane sealants, and fluorocarbon polymers. 
     
     
         18 . A die block according to  claim 9 , wherein said sealant is selected from the group consisting polysiloxanes, urethane sealants and fluorocarbon polymers. 
     
     
         19 . Process for forming a nonwoven web comprising melt-blown fibers according to  claim 12 , wherein in said step of providing a thermoplastic polymer for forming melt-blown fibers, the thermoplastic polymer is polypropylene, exhibiting a MFI from 30 to 2000 for 10 minutes at 2.16 kg at 210° C. or polyethylene exhibiting a MFI from 30 to 2000 for 10 minutes at 2.16 kg at 190° C. 
     
     
         20 . Process for forming a nonwoven web comprising melt-blown fibers according to  claim 12 , wherein in said step of forming filaments the pressure applied at the polymer supply is at less than 45 bar.