Process and apparatus for the production of a bulky spunbond nonwoven fabric

Abstract

A process for producing a nonwoven fabric comprises the steps of a spinneret extruding a plurality of filaments, cooling the filaments with one or more cooling elements arranged below the spinneret, drawing the filaments in a drawing duct and laying the filaments on a movable support to form a nonwoven fabric. The process further comprises suctioning gas in a first suction device, heating the nonwoven fabric using a heated calender downstream of the first suction device to consolidate the filaments of the nonwoven fabric and to cause an increase in volume of the nonwoven fabric, suctioning gas below the movable support with a higher second suction speed, in a second suction device downstream of the heated calender, and suctioning gas below the movable support in a third suction region with a third suction speed lower than the second suction speed, by a shutter with one or more adjustable openings.

1 . A process for producing a nonwoven fabric ( 150 ), comprising the steps of:
 (a) extruding a plurality of filaments ( 100 ) using a spinneret ( 11 );   (b) cooling said filaments ( 100 ) using one or more cooling elements ( 15 , 15 ′) arranged below said spinneret ( 11 );   (c) drawing said filaments ( 100 ) in a drawing duct ( 17 ) arranged below said one or more cooling elements ( 15 , 15 ′);   (d) laying said filaments ( 100 ) on a movable support ( 28 ) arranged below said drawing duct ( 17 ), along a feed direction (D) in order to form a nonwoven fabric ( 150 );   (e) suctioning gas with a first suction speed using a first suction device ( 31 ) in a first suction region ( 30 ) below said movable support ( 28 );   (f) heating the nonwoven fabric ( 150 ) using a heated calender ( 11   a ,  11   b ) arranged downstream of the first suction region ( 30 ) to consolidate the said filaments of said nonwoven fabric ( 150 ) and to cause a volume increase in said nonwoven fabric ( 150 );   (g) suctioning gas below said movable support ( 28 ) with a second suction speed higher than said first suction speed, in a second suction region ( 40 ) arranged downstream of the heated calender ( 11   a ,  11   b ), using a second suction device ( 41 ); and   (h) suctioning gas below said movable support ( 28 ) in a third suction region ( 50 ) with a third suction speed lower than the second suction speed and obtained using a shutter ( 51 ) equipped with one or more openings ( 52 ), the opening degree of said one or more openings being adjustable.   
     
     
         2 . The process according to  claim 1 , wherein the third suction speed progressively decreases. 
     
     
         3 . The process according to  claim 1 , wherein the first and second suction speeds are between 10 m/s and 50 m/s. 
     
     
         4 . The process according to  claim 1 , wherein during said step (f), the temperature of the heated calender ( 11   a ,  11   b ) is between 40° C. and 180° C. 
     
     
         5 . The process according to  claim 1 , wherein during said step (b), said one or more cooling elements ( 15 , 15 ′) provide gas having a temperature between 10° C. and 50° C. 
     
     
         6 . The process according to  claim 1 , wherein in said step (d) the drawn filaments are laid at the first suction region ( 30 ). 
     
     
         7 . The process according to  claim 1 , wherein the filaments are bicomponent filaments. 
     
     
         8 . An apparatus ( 10 ) for producing a nonwoven fabric ( 150 ), said apparatus comprising:
 a spinneret ( 11 ) adapted to extrude a plurality of filaments ( 100 ) and comprising an extrusion surface ( 2   a );   one or more cooling elements ( 15 ,  15 ′) adapted to cool said plurality of filaments downstream of the spinneret ( 11 ), said one or more cooling elements adapted to direct a gas against said plurality of filaments;   a drawing channel ( 17 ) arranged downstream of said one or more cooling elements ( 15 , 15 ′) and adapted to draw said plurality of filaments ( 100 );   a movable support ( 28 ), permeable to gases and adapted to collect said drawn plurality of filaments so as to form a nonwoven fabric and configured to move said nonwoven fabric along a feed direction (D);   a heated calender ( 11   a ,  11   b ) adapted to heat said nonwoven fabric ( 150 ) and cause an increase in the volume of said nonwoven fabric ( 150 );   a first suction device ( 31 ) adapted to define a first suction region ( 30 ) upstream of said heated calender with respect to the feed direction (D);   a second suction device ( 41 ) adapted to define at least one second suction region ( 40 ) downstream of the heated calender, and   a shutter ( 51 ) equipped with one or more openings ( 52 ) for the passage of gas, the shutter being adapted to define a third suction region ( 50 ) arranged downstream of said second suction region ( 40 ).   
     
     
         9 . The apparatus according to  claim 8 , wherein the shutter ( 51 ) is fluidically connected to said second suction device ( 41 ). 
     
     
         10 . The apparatus according to  claim 9 , wherein the openings ( 52 ) are adjustable to different opening degrees. 
     
     
         11 . The apparatus as in  claim 10 , wherein the openings are adjustable using an anemometer or Pitot tube. 
     
     
         12 . The apparatus as in  claim 8 , wherein the gas is air. 
     
     
         13 . The apparatus as in  claim 9 , wherein the gas is air and the openings are adjustable using an anemometer. 
     
     
         14 . The process according to  claim 2 , wherein the first and second suction speeds are between 10 m/s and 50 m/s. 
     
     
         15 . The process according to  claim 14 , wherein during said step (f), the temperature of the heated calender ( 11   a ,  11   b ) is between 40° C. and 180° C. 
     
     
         16 . The process according to  claim 2 , wherein during said step (b), said one or more cooling elements ( 15 , 15 ′) provide gas having a temperature between 10° C. and 50° C. and/or a speed between 2 m/s and 60 m/s. 
     
     
         17 . The process according to  claim 5 , wherein during said step (b), said one or more cooling elements ( 15 , 15 ′) provide gas having a speed between 2 m/s and 60 m/s. 
     
     
         18 . The process according to  claim 2 , wherein in said step (d) the drawn filaments are laid at the first suction region ( 30 ) and the filaments are bicomponent filaments.