Method for perforating nonwoven fabric
The present invention relates to the perforation of nonwovens with a perforating roll and an opposing roll. The perforating roll and opposing roll form a gap, through which a nonwoven being perforated, is guided and perforated. The perforation apparatus comprises a feed device and a withdrawal device. The feed device is arranged such that the nonwoven being perforated advances first onto the opposing roll, before it enters the gap. The withdrawal device is arranged such that after leaving the gap, the perforated nonwoven remains on the perforating roll. Furthermore, a perforation method and a corresponding nonwoven structure are provided.
1. A method of perforating a nonwoven, comprising
advancing a nonwoven from a feed device to a gap between a perforating roll and an opposing roll, wherein the opposing roll is heated to a temperature that is at least 40° C. higher than that of the perforating roll;
as the nonwoven enters the gap, directing the nonwoven to loop the opposing roll at an angle greater than 45°;
between the feed device and the opposing roll, preliminarily elongating the nonwoven between 1.5% and 10%, before it loops the opposing roll;
perforating the nonwoven in the gap;
after having been perforated, advancing the nonwoven from the gap to a withdrawal device.
2. The method of claim 1 , further comprising, after the perforating step, directing the nonwoven to loop the perforating roll at an angle of at least 45°.
3. The method of claim 2 , wherein the nonwoven is directed to loop the perforating roll at an angle between 90° and 270°.
4. The method of claim 1 , wherein the perforating step comprises forming perforations that are approximately circular.
5. The method of claim 4 , wherein the perforations have a ratio of axes in the machine direction to cross direction of from 1 to 1.18.
6. The method of claim 1 , wherein the nonwoven is subjected to a level of tension between the feed device and the opposing roll that is greater than a level of tension between the perforating roll and the withdrawal device.
7. The method of claim 1 , further comprising the step of frictionally setting the nonwoven as it passes between the gap such that the nonwoven is stabilized during perforation.
8. The method of claim 1 , wherein the elongated nonwoven sheet material loops the opposing roll at an angle greater than 90°.
9. A method of perforating a nonwoven, comprising:
elongating a nonwoven sheet material between 1.5% and 10%;
looping the elongated nonwoven sheet material over a first roll at an angle greater than 45°;
passing the elongated sheet material through a gap between the first roll and a second roll having a plurality of needles; and
perforating the elongated sheet material as it passes through the gap, and wherein the first roll is heated to a temperature that is at least 40° C. higher than that of the second roll.
10. The method of claim 9 , further comprising the step of looping the elongated nonwoven sheet material over second roll at an angle of at least 45° following the perforation step.
11. The method of claim 9 , wherein the elongated nonwoven sheet material loops the first roll at an angle greater than 90°.
12. The method of claim 9 , wherein the nonwoven is directed to loop the second roll at an angle between 90° and 270°.
13. The method of claim 9 , wherein the perforating step comprises forming perforations that are approximately circular.
14. The method of claim 13 , wherein the perforations have a ratio of axes in the machine direction to cross direction of from 1 to 1.18.
15. The method of claim 9 , wherein the nonwoven is subjected to a level of tension between a feed device and the opposing roll that is greater than a level of tension between the perforating roll and a withdrawal device.
16. The method of claim 9 , further comprising the step of frictionally setting the nonwoven as it passes between the gap such that the nonwoven is stabilized during perforation.