Method for preparing a nonwoven web
The present invention relates to a method for producing a nonwoven fabric. The method according to the invention comprises forming a nonwoven web using a wet lay forming process, hydroentangling the web and providing the web with a high quality hydroembossed pattern. The invention also concerns a nonwoven fabric exhibiting a three dimensional pattern, which remains even in wet wipes prepared from the material.
1. A method for producing a nonwoven fabric comprising a three-dimensional pattern thereon, the method comprising:
forming a first web from an aqueous suspension of fibers on a wire support;
hydroentangling the first web to provide a self-supporting web;
transferring the self-supporting web from the wire support to a hydroembossing roll in a way in which the self-supporting web supports itself during the transfer;
hydroembossing the self-supporting web via the hydroembossing roll, the hydroembossing roll comprising a sleeve associated with the roll, the sleeve having a negative impression of the three-dimensional pattern within a body thereof, wherein the hydroembossing comprises moving a portion of the fibers of the self-supporting web into the negative impression of the sleeve to form the three-dimensional pattern on the self-supporting web; and
drying the self-supporting web to provide the nonwoven fabric comprising the three-dimensional pattern thereon.
2. The method of claim 1 , further comprising hydroentangling the first web with one or more additional unwound webs.
3. The method of claim 1 , wherein the sleeve is detachable from the roll.
4. The method according to claim 1 , wherein the aqueous suspension is laid on the wire support on top of a second unwound web of a spunbond, spunlace, wetlaid or tissue type.
5. The method according to claim 4 , wherein a third unwound web of a spunbond, spunlace, wetlaid or tissue type is further laid on top of the second web.
6. The method according to claim 1 , wherein the aqueous suspension comprises both short cut regenerated fibers and natural fibers.
7. The method according to claim 1 , wherein a height of the three-dimensional pattern on the nonwoven fabric comprises at least 200 μm between a minimum and maximum thickness of the nonwoven fabric.
8. The method of claim 1 , wherein the hydroentangling is done at a speed of 500-1100 ft/min, a nozzle pressure of 1200 psi, with a nozzle size of 80-150 micron, and at a vacuum pressure of 1-450 mbar.
9. The method of claim 1 , wherein during the hydroembossing, excess water is removed through openings in the hydroembossing roll.
10. The method according to claim 1 , wherein in the nonwoven fabric, an angle of inclination from a minimum thickness to a maximum thickness of the nonwoven fabric is in a range 48°-90°.
11. The method according to claim 1 , wherein areas of the nonwoven fabric comprising the patterned area comprise at least 10% more fibers by weight than non-patterned areas of the nonwoven fabric.
12. The method according to claim 1 , wherein the self-supporting web comprises a mixture of pulp and regenerated fibers.
13. The method according to claim 1 , wherein the pattern comprises a machine readable code.
14. The method according to claim 1 , wherein a tensile strength of the web following the hydroentangling and prior to removal from the wire support is at least 200 g/25 mm for single layer products.
15. The method according to claim 1 , wherein a tensile strength of the web following the hydroentangling and prior to removal from the wire support is at least 200 g/25 mm for multilayered products.
16. A method for producing a nonwoven fabric comprising a three-dimensional pattern thereon, the method comprising:
forming a first web from an aqueous suspension of fibers on a wire support;
hydroentangling the first web to provide a self-supporting web;
removing the self-supporting web from the wire support;
hydroembossing the self-supporting web via a hydroembossing roll comprising a sleeve associated with the roll, the sleeve having a negative impression of the three-dimensional pattern within a body thereof, wherein the hydroembossing comprises moving a portion of the fibers of the self-supporting web into the negative impression of the sleeve to form the three-dimensional pattern on the self-supporting web; and
drying the self-supporting web to provide the nonwoven fabric comprising the three-dimensional pattern thereon,
wherein the hydroentangling is done at a speed of 500-1100 ft/min, a nozzle pressure of 1-1200 psi, with a nozzle size of 80-150 micron, and at a vacuum pressure of 1-450 mbar.