Fiber Forming Device and Process Using Same

Abstract

A fiber forming device is disclosed that is well suited to producing nonwoven webs having excellent barrier properties. In one aspect, the fiber forming device can be used to produce meltblown webs or coform webs. The fiber forming device includes a die head containing multiple rows of polymer nozzles for forming fibers. Air flow paths are positioned on either side of the rows of polymer nozzles. In addition, an air flow path is positioned in between the rows of polymer nozzles. The air flow paths produce an attenuating gas stream that attenuates fibers being produced by the polymer nozzles and directs the fibers onto a forming surface for forming nonwoven webs.

1 - 13 . (canceled) 
     
     
         14 . A process for forming a nonwoven web comprising:
 forming two rows of fibers from a molten polymer material;   contacting the fibers with a plurality of gas streams for attenuating the fibers, the gas streams including a first gas stream that impinges on a first row of fibers from a first side, a second gas stream that impinges on a second row of fibers from a second side, and a third gas stream that is directed between and impinges on the first row of fibers and the second row of fibers, the first gas stream being emitted by a first air flow path at a first pressure, the second gas stream being emitted by a second air flow path at a second pressure, and the third gas stream being emitted by a third air flow path at a third pressure, and wherein the third pressure is greater than the first pressure and the second pressure; and   depositing the attenuated fibers onto a forming surface for forming a nonwoven web.   
     
     
         15 . The process as defined in  claim 14 , wherein the third pressure of the third gas stream is at a pressure ratio of the first pressure to the first gas stream of from about 1.05:1 to about 2:1. 
     
     
         16 . The process as defined in  claim 15 , wherein the third pressure of the third gas stream is at a pressure ratio of the second pressure to the second gas stream of from about 1.05:1 to about 2:1. 
     
     
         17 . The process as defined in  claim 14 , wherein the polymer material comprises a polyolefin polymer, such as a polypropylene polymer. 
     
     
         18 . The process as defined in  claim 14 , wherein the polymer material comprises a biodegradable polymer. 
     
     
         19 . The process as defined in  claim 14 , wherein the two rows of fibers are parallel, the process further comprising the step of contacting the two parallel rows of fibers with a liquid absorbent material prior to the fibers being deposited onto the forming surface for forming a coform web. 
     
     
         20 . The process as defined in  claim 14 , wherein the two rows of fibers are emitted via a die head having a length and a width, the die head comprising a first row of polymer nozzles and a second row of polymer nozzles, wherein the first row of fibers are emitted from the first row of polymer nozzles and the second row of fibers are emitted from the second row of polymer nozzles and wherein the first row of polymer nozzles and the second row of polymer nozzles are each positioned at an angle towards each other, wherein the die head includes a vertical axis that extends from a top of the die head to a bottom of the die head and includes a horizontal axis that is perpendicular to the vertical axis and wherein the first row of polymer nozzles are positioned at an acute angle relative to the vertical axis and the second row of polymer nozzles are positioned at an acute angle relative to the vertical axis. 
     
     
         21 . The process as defined in  claim 14 , wherein the first pressure, the second pressure, and the third pressure are all maintained below about 10 psi. 
     
     
         22 . The process as defined in  claim 14 , wherein the attenuated fibers deposited onto the forming surface have a fiber diameter of less than about 5 microns. 
     
     
         23 . The process as defined in  claim 14 , wherein the two rows of fibers are emitted via a die head having a length and a width, the die head comprising a first row of polymer nozzles and a second row of polymer nozzles, wherein the die head includes a fiber dispensing surface, the first row of polymer nozzles and the second row of polymer nozzles being disposed along the fiber dispensing surface, similarly, the first air flow path, the second air flow path, and the third air flow path are also disposed along the fiber dispensing surface, the fiber dispensing surface having a V-shape defining an apex, and wherein the first row of polymer nozzles and the second row of polymer nozzles are positioned to emit polymer fibers adjacent to the apex of the fiber dispensing surface. 
     
     
         24 . The process as defined in  claim 14 , wherein the first air flow path and the second air flow path are each positioned at an angle towards each other. 
     
     
         25 . The process as defined in  claim 24 , wherein the two rows of fibers are emitted via a die head having a length and a width, the die head comprising a first row of polymer nozzles and a second row of polymer nozzles, wherein the die head includes a vertical axis that extends from a top of the die head to a bottom of the die head and includes a horizontal axis that is perpendicular to the vertical axis and wherein the first air flow path is positioned at an acute angle relative to the horizontal axis and the second air flow path is positioned at an acute angle relative to the horizontal axis. 
     
     
         26 . The process as defined in  claim 14 , wherein the third air flow path is positioned to emit a gas in a downward, vertical direction. 
     
     
         27 . The process as defined in  claim 14  further comprising maintaining gas pressure through the third air flow path above a pressure of a gas exiting the first air flow path and of a gas exiting the second air flow path. 
     
     
         28 . The process as defined in  claim 27 , wherein the gas pressure through the third air flow path is maintained via a fluid flow regulator in communication with the gas flow path to the third air flow path. 
     
     
         29 . The process as defined in  claim 14 , wherein the two rows of fibers are emitted via a die head having a length and a width, the die head comprising a first row of polymer nozzles and a second row of polymer nozzles, wherein the first air flow path and the first row of polymer nozzles are symmetrical to the second air flow path and the second row of polymer nozzles with respect to a vertical axis of the die head. 
     
     
         30 . The process as defined in  claim 14 , wherein the two rows of fibers are emitted via a die head having a length and a width, the die head comprising a first row of polymer nozzles and a second row of polymer nozzles, wherein the first and second air flow paths comprise slots that extend along the length of the die head or comprise a row of apertures that extend along the length of the die head. 
     
     
         31 . The process as defined in  claim 14 , wherein the first air flow path is in fluid communication with a first air chamber, the second air flow path is in fluid communication with a second air chamber, and the third air flow path is in fluid communication with a third air chamber, the first, second and third air chambers being isolated from each other, each of the first, second and third air chambers being in communication with a pressurized gas source for providing a pressurized gas to each of the first, second and third air flow paths. 
     
     
         32 . The process as defined in  claim 14 , wherein the third air flow path is in fluid communication with a wedge-shaped flow control device for directing flow of a gas through the third air flow path while preventing turbulence. 
     
     
         33 . A process for forming a nonwoven web comprising:
 forming two rows of fibers from a molten polymer material;   contacting the fibers with a plurality of gas streams for attenuating the fibers, the gas streams including a first gas stream that impinges on a first row of fibers from a first side, a second gas stream that impinges on a second row of fibers from a second side, and a third gas stream that is directed between and impinges on the first row of fibers and the second row of fibers, the first gas stream being emitted by a first air flow path, the second gas stream being emitted by a second air flow path, and the third gas stream being emitted by a third air flow path;   maintaining gas pressure through the third air flow path above a pressure of a gas exiting the first air flow path and of a gas exiting the second air flow path, wherein the gas pressure through the third air flow path is maintained via a fluid flow regulator in communication with the gas flow path to the third air flow path; and   depositing the attenuated fibers onto a forming surface for forming a nonwoven web.