Stretchable multiple-component nonwoven fabrics and methods for preparing
View Patent ↗A method for preparing stretchable bonded nonwoven fabrics which involves forming a substantially nonbonded nonwoven web of multiple-component continuous filaments or staple fibers which are capable of developing three-dimensional spiral crimp, activating the spiral crimp by heating substantially nonbonded web under free shrinkage conditions during which the nonwoven remains substantially nonbonded, followed by bonding the crimped nonwoven web using an array of discrete mechanical, chemical, or thermal bonds. Nonwoven fabrics prepared according to the method of the current invention have an improved combination of stretch-recovery properties, textile hand and drape compared to multiple-component nonwoven fabrics known in the art.
1. A method for preparing a stretchable nonwoven fabric which comprises the steps of:
providing a substantially nonbonded nonwoven web comprising multiple-component fibers, the multiple-component fibers being capable of developing three-dimensional spiral crimp upon heating;
conveying the substantially nonbonded nonwoven web on a first conveying surface having a first conveying speed;
transferring the substantially nonbonded nonwoven web from the first conveying surface through a transfer zone to a second conveying surface, the second conveying surface having a second conveying speed; the substantially nonbonded nonwoven web being conveyed through the transfer zone in such a way that the substantially nonbonded nonwoven web does not contact a conveying surface in the transfer zone;
heating the substantially nonbonded nonwoven web in the transfer zone to a temperature sufficient to cause the multiple-component fibers to develop three-dimensional spiral crimp resulting in an area shrinkage of the substantially nonbonded nonwoven web and a decrease in the speed of the web as it is conveyed through the transfer zone, the heating temperature being selected such that the nonwoven web remains substantially nonbonded during the heating step;
transferring the heat-treated substantially nonbonded nonwoven web to the second conveying surface as the web exits the transfer zone, the second conveying speed being less than the first conveying speed and the second conveying speed being selected to be approximately equal to the speed of the heat-treated substantially nonbonded nonwoven web as the web contacts the second conveying surface upon exiting the transfer zone; and
bonding the heat-treated substantially nonbonded nonwoven web with an array of discrete bonds to form the stretchable multiple-component bonded nonwoven fabric.
2. The method of claim 1 , wherein the substantially nonbonded nonwoven web is allowed to free fall through the transfer zone.
3. The method of claim 1 , wherein the substantially nonbonded nonwoven web is floated on a gas as it is conveyed through the transfer zone.
4. The method of claim 1 wherein the area shrinkage of the substantially nonbonded nonwoven web is substantially complete as the web exits the transfer zone.
5. A method for preparing a stretchable nonwoven fabric which comprises the steps of:
providing a substantially nonbonded nonwoven web comprising multiple-component fibers capable of developing three-dimensional spiral crimp upon heating;
conveying the substantially nonbonded nonwoven web on a first conveying surface having a first conveying speed;
transferring the substantially nonbonded nonwoven web through a transfer zone to a second conveying surface, the second conveying surface having a second conveying speed and the substantially nonbonded nonwoven web having a nonwoven surface speed which decreases as the substantially nonbonded nonwoven is conveyed through the transfer zone;
conveying the substantially nonbonded nonwoven web through the transfer zone on a series of at least two driven rolls, each of the driven rolls having a peripheral linear speed, the peripheral linear speed of the rolls progressively decreasing as the web moves through the transfer zone in such a way that the peripheral linear speed of each roll is approximately equal to the speed of the nonwoven web as it contacts each roll;
heating the substantially nonbonded nonwoven web in the transfer zone to a temperature sufficient to cause the multiple-component fibers to develop three-dimensional spiral crimp resulting in an area shrinkage of the substantially nonbonded web so as to decrease the speed of the nonwoven web as it is conveyed through the transfer zone, the heating temperature being selected such that the nonwoven web remains substantially nonbonded during the heating step;
transferring the heat-treated substantially nonbonded nonwoven web to the second conveying surface as the web exits the transfer zone, the second conveying speed being less than the first conveying speed and the second conveying speed being selected to be approximately equal to the speed of the heat-treated substantially nonbonded nonwoven web as the web contacts the second conveying surface upon exiting the transfer zone; and
bonding the heat-treated substantially nonbonded nonwoven web with an array of discrete bonds to form the stretchable bonded nonwoven fabric.
6. The method of claim 5 , wherein the peripheral linear speed of adjacent rolls varies by less than 20%.
7. The method of claim 5 , wherein the peripheral linear speed of adjacent rolls varies by less than 10%.
8. The method of claim 5 , wherein the area shrinkage of the substantially nonbonded web is substantially complete as the web exits the transfer zone.