Process and apparatus for producing a voluminous nonwoven fabric

Abstract

Provided is a process for producing a nonwoven fabric. The process includes extruding a plurality of filaments from a spinneret, the filaments being at least bicomponent filaments; depositing the filaments to form a nonwoven fabric on an element collecting the filaments; performing a bonding of the nonwoven fabric; increasing the thickness of the nonwoven fabric by crimping at least part of the filaments by heating the nonwoven fabric; and, preferably performing a setting of the nonwoven fabric, wherein the bonding and the increasing the thickness steps are performed substantially simultaneously by means of a heated calendar. Also provided is the nonwoven fabric formed using the process and an apparatus for carrying out the process.

1 . A process for producing a nonwoven fabric ( 150 ), comprising the steps of:
 (a) extruding a plurality of filaments ( 100 ) from a spinneret ( 1   a ), said filaments being at least bicomponent filaments;   (b) depositing said filaments ( 100 ) to form a nonwoven fabric ( 150 ) on an element collecting the filaments;   (c) performing a bonding of said nonwoven fabric ( 150 );   (d) increasing the thickness (H 2 ) of said nonwoven fabric ( 150 ) by crimping at least part of the filaments ( 100 ) by heating said nonwoven fabric ( 150 ); and   (e) performing a setting of said nonwoven fabric ( 150 );   wherein said steps (c) and (d) are performed substantially simultaneously by means of a heated calendar ( 20 ).   
     
     
         2 . The process according to  claim 1 , wherein the composition of the nonwoven fabric treated by the calendar in said step (d) is substantially homogeneous. 
     
     
         3 . The process according to  claim 1 , wherein said filaments ( 100 ) of the nonwoven fabric have same composition, so that they can be crimped by the heated calendar ( 20 ) in said step (d). 
     
     
         4 . The process according to  claim 1 , wherein said calendar is configured to define, on the nonwoven fabric, a bonding area between 5% and 25%. 
     
     
         5 . The process according to  claim 1 , wherein said calendar has a plurality of protrusions ( 21 ) comprising between 4 and 50 protrusions per cm 2 . 
     
     
         6 . The process according to  claim 1 , wherein said calendar is heated to a temperature higher than 130° C. 
     
     
         7 . The process according to  claim 1 , further comprising a step of cooling said nonwoven fabric ( 150 ) following said step (d). 
     
     
         8 . The process according to  claim 7 , wherein said cooling step is performed by cooling means ( 5 ,  8 ) comprising at least one of:
 a cooling device ( 5 ) configured to direct a gas flow (G 3 ) against said nonwoven fabric ( 150 ) at a temperature between 30 and 140° C.   a suction roller;   a cooled conveyor belt ( 8 ).   
     
     
         9 . The process according to  claim 1 , wherein said setting step (e) comprises additional calendaring. 
     
     
         10 . The process according to  claim 1 , wherein during said step (a), a plurality of bicomponent filaments ( 100 ) comprising two sub-filaments ( 100   a ,  100   b ) adhered to each other are extruded, said two sub-filaments ( 100   a ,  100   b ) being extruded according to a side-by-side configuration, so as to form a contact surface ( 105 ) between said two sub-filaments which, in cross-section of the filament, has a substantially wave-like shape,
 said two sub-filaments ( 100   a ,  100   b ) made of materials having different melting temperatures and/or different viscosities, said temperature difference being at least 10° C. and said viscosity difference being greater than 20%.   
     
     
         11 . A calendar ( 20 ) for the treatment of nonwoven fabrics, comprising heating elements ( 200 ) and configured to define, on a nonwoven fabric, a bonding area between 5% and 25%, said calendar comprising a number between 4 and 50 protrusions per cm 2 . 
     
     
         12 . A method comprising using the calendar according to  claim 11  to crimp the filaments of a nonwoven fabric in which all the filaments have the same composition. 
     
     
         13 . Apparatus ( 10 ) for producing a nonwoven fabric ( 150 ), comprising a device ( 1 ) for extruding filaments ( 100 ) equipped with a spinneret (la) for extruding a plurality of filaments ( 100 ), collecting means ( 2 ) to collect the filaments ( 100 ) and form a nonwoven fabric ( 150 ), a calendar ( 20 ) heated according to  claim 11 , and an additional setting device ( 7 ). 
     
     
         14 . The apparatus ( 10 ) according to  claim 13 , wherein the heated calendar ( 20 ) is arranged immediately downstream of the device ( 1 ) for extruding filaments ( 100 ), so that the nonwoven fabric does not undergo thermal and/or bonding treatments between the device ( 1 ) for extruding filaments ( 100 ) and the heated calendar ( 20 ). 
     
     
         15 . A nonwoven fabric ( 150 ) obtainable by a process according to  claim 1 , wherein said nonwoven fabric ( 150 ) comprises a number of constrained areas ( 2011 ) between 4 and 50 per cm 2 , to define a bonding area between 5% and 25%. 
     
     
         16 . The nonwoven fabric ( 150 ) according to  claim 15 , wherein said nonwoven fabric ( 150 ) comprises a number of constrained areas ( 2011 ) between 5 and 30 per cm 2  to define a bonding area between 7% and 18%. 
     
     
         17 . The process according to  claim 2 , wherein all said filaments ( 100 ) of the nonwoven fabric have same composition and said calendar is configured to define, on the nonwoven fabric, a bonding area between 7% and 18%. 
     
     
         18 . The process according to  claim 2 , wherein said calendar has a plurality of protrusions ( 21 ), the number of said protrusions ( 21 ) being between 4 and 40 protrusions per cm 2 , said calendar is heated to a temperature higher than 160° C. and further comprising a step of cooling said nonwoven fabric ( 150 ) following said step (d). 
     
     
         19 . The process according to  claim 4 , wherein said calendar has a plurality of protrusions ( 21 ), the number of said protrusions ( 21 ) being between 4 and 40 protrusions per cm 2 , said calendar is heated to a temperature higher than 160° C. and further comprising a step of cooling said nonwoven fabric ( 150 ) following said step (d). 
     
     
         20 . The process according to  claim 8 , wherein during said step (a), a plurality of bicomponent filaments ( 100 ) comprising two sub-filaments ( 100   a ,  100   b ) adhered to each other are extruded, said two sub-filaments ( 100   a ,  100   b ) being extruded according to a side-by-side configuration to form a contact surface ( 105 ) between said two sub-filaments which, in cross-section of the filament, has a substantially wave-like shape,
 said two sub-filaments ( 100   a ,  100   b ) made of materials having different melting temperatures and/or different viscosities, said temperature difference being at least 10° C. and said viscosity difference being greater than 20%.