Device and method for melt spinning fine non-woven fibers

Abstract

A meltblown method for melt spinning fine non-woven fibers and a device for carrying out said method. According to the invention, a polymer melt is extruded, in order to form several fiber strands, through several nozzle bores of a spinning nozzle and twisted on the outlet side of the nozzle bores by means of a cold blow flow. According to the invention, the blow flow is fed to the fiber strands in an acceleration path wherein the fiber stands and the blow flow are accelerated in such a manner that the fiber strands are twisted in order to form continuous fine fibers. According to the inventive device, the inventive acceleration path is formed between the upper edges and the lower edges of the two blow nozzle openings below the spinning nozzle.

1 . A melt-blown method for melt spinning fine non-woven fibers, comprising: 
 extruding a polymer melt through several nozzle holes of a spinneret in order to form several fiber strands; and    immediately after emerging from the nozzle holes, acting on the fiber strands with a cold blowing stream that, subject to the action of an overpressure, flows through at least one blowing nozzle orifice onto the fiber strands and draws the fiber strands,    wherein the blowing stream is guided to the fiber strands inside an acceleration section, in which the fiber strands and the blowing stream are accelerated in such a manner that the fiber strands are drawn to form endless microfibers.    
   
   
       2 . The method as claimed in  claim 1 , wherein the overpressure of the blowing stream is set to a value of less than or equal to about 1,000 mbar.  
   
   
       3 . The method as claimed in  claim 1 , wherein the blowing stream is produced from air that exhibits a natural air temperature in a range between about 15° C. and about 120° C.  
   
   
       4 . The method as claimed in  claim 3 , wherein the blowing stream is produced from the surrounding air at an ambient temperature, the surrounding air being drawn in from the environment below the spinneret.  
   
   
       5 . The method as claimed in  claim 1 , wherein the fiber strands are extruded at a mass flow of the polymer melt through the nozzle holes of the spinneret in the range of about 1.0 g/min. to about 10 g/min. per nozzle hole.  
   
   
       6 . The method as claimed in  claim 5 , wherein the mass flow is greater than about 3 g/min. per nozzle hole.  
   
   
       7 . The method as claimed in  claim 1 , wherein before emerging from the nozzle hole, the polymer melt is heated to a temperature in a range between about 300° C. and about 400° C.  
   
   
       8 . The method as claimed in  claim 1 , wherein a length of the acceleration section for accelerating the blowing stream and the fiber strands ranges from about 2 mm to about 30 mm.  
   
   
       9 . The method as claimed in  claim 8 , wherein the acceleration section adjoins directly the mouth of the nozzle holes without any spacing.  
   
   
       10 . The method as claimed in  claim 8 , wherein the acceleration section adjoins directly the mouth of the nozzle holes at a short distance in the range of a maximum of about 2 mm.  
   
   
       11 . The method as claimed in  claim 1 , wherein after passing through the acceleration section, the fiber strands and the blowing stream are fed into a free space, the free space exhibiting a pressure that is approximately equal to the ambient pressure.  
   
   
       12 . The method as claimed in  claim 11 , wherein additional zones of air turbulence, acting on the fibers, are generated by at least one air conductor inside the free space.  
   
   
       13 . The method as claimed in  claim 1 , wherein the fibers are cooled and guided by means of an air stream, supplied below the acceleration section.  
   
   
       14 . The method as claimed in  claim 1 , wherein a fiber fineness of the endless microfibers lies in a range between about 0.5 μm and about 30 μm.  
   
   
       15 . The method as claimed in  claim 1 , wherein the microfibers are deposited to form a non-woven fabric.  
   
   
       16 . A device for melt spinning fine non-woven fibers, the device comprising: 
 a spinneret, the underside of which exhibits a plurality of nozzle holes configured in rows;    and a blower, which exhibits two blowing nozzle orifices, which lie opposite each other, each of the blowing nozzle orifices being formed between an upper edge and a bottom edge, both of which extend substantially parallel to the nozzle holes, wherein an acceleration section is formed between the upper edges and the bottom edges of the two blowing nozzle orifices below the spinneret, and wherein in the acceleration section the fiber strands and the blowing stream are accelerated in such a manner that the fiber strands are drawn into endless microfibers.    
   
   
       17 . The device as claimed in  claim 14 , wherein an exit throat is formed between the bottom edges of the two blowing nozzle orifices, and an entry throat is formed between the upper edges of the two blowing nozzle orifices, wherein the exit throat exhibits a free flow cross section that is smaller than a flow cross section of the entry throat.  
   
   
       18 . The device as claimed in  claim 15 , wherein an exit throat exhibits a slit width in a range between about 2 mm and about 8 mm.  
   
   
       19 . The device as claimed in  claim 17 , wherein the entry throat is constructed on a level with the bottom side of the spinneret.  
   
   
       20 . The device as claimed in  claim 17 , wherein the entry throat is constructed at a short distance from the bottom side of the spinneret.  
   
   
       21 . The device as claimed in  claim 17 , wherein the entry throat and the exit throat define the length of the acceleration section, which lies in a range between about 2 mm and about 30 mm.  
   
   
       22 . The device as claimed in  claim 14 , wherein the bottom edge and the upper edge, which are assigned to one of the blowing orifices, form between themselves an inflow channel for the air feed, and wherein the inflow channel in the direction of the blowing orifice exhibits a tapering flow cross section.  
   
   
       23 . The device as claimed in  claim 16 , wherein the blowing orifices are connected to at least one pressure chamber, in which the air is held under overpressure.  
   
   
       24 . The device as claimed in  claim 23 , wherein the pressure chamber is connected to a suction unit, by means of which surrounding air is drawn in and conveyed into the pressure chamber.  
   
   
       25 . The device as claimed in  claim 16 , wherein a free space is formed below the bottom edges of the blowing nozzles.  
   
   
       26 . The device as claimed in  claim 25 , wherein the free space exhibits additional aids for at least one of guiding, cooling, or drawing the fibers.  
   
   
       27 . Non-woven fibers made of a polymer material and produced by means of a melt-blown method as claimed in  claim 1 , the microfibers comprising an endless length, whereby a fiber fineness of the endless microfibers lies in a range between about 0.5 μm and about 30 μm.  
   
   
       28 . A non-woven fabric made of non-woven fiber, the fibers produced by means of a melt-blown method as claimed in  claim 1  and exhibiting an endless length, whereby a fiber fineness of the endless microfibers lies in a range between about 0.5 μm and about 30 μm.  
   
   
       29 . The non-woven fabric as claimed in  claim 28 , wherein the endless microfibers are deposited to form a weight per unit of area in a range between about 1.5 g/m 2  and about 50 g/m 2  and lead to an elongation at break of at least about 60%.  
   
   
       30 . A composite non-woven fabric, comprising several layers of non-woven fabric, wherein at least one of the layers is made of a non-woven fabric exhibiting the endless microfibers as claimed in  claim 24 .  
   
   
       31 . The composite non-woven fabric as claimed in  claim 30 , wherein the non-woven fabric of the layer exhibits a weight per unit of area in a range between about 1.5 g/m 2  and about 50 g/m 2  and exhibits an elongation at break of at least about 60%.  
   
   
       32 . The composite non-woven fabric as claimed in  claim 30 , wherein at least one other layer is made of a spun bond non-woven fabric.