Sheet of loop material, method and apparatus for forming same
A sheet of loop material having utility as the landing zone in the manufacture of, e.g. disposable diapers and having excellent properties and an exceptionally low basis weight. Methods and apparatus for forming the sheet of loop material are also disclosed.
1. A method of treating a sheet of loop material, comprising:
providing a sheet of loop material adapted to be cut into pieces to form loop portions for fasteners comprising releasably engageable hook and loop portions, said sheet of loop material comprising:
a backing comprising a thermoplastic backing layer and having front and rear major surfaces; and
a sheet of fibers having generally non-deformed anchor portions bonded in the thermoplastic backing layer at bonding locations spaced along the backing layer, and arcuate portions projecting from the front surface of the backing between the bonding locations;
passing the sheet of loop material between a pair of interdigitated rollers so as to stretch at least a portion of the backing layer beyond its elastic limit in a first direction;
elongating the sheet of loop material in the first direction 50% to 150%; and
annealing the sheet of loop material so as to stabilize it in its elongated condition.
2. The method according to claim 1 wherein the sheet of loop material is in the form of a web of indefinite length.
3. The method according to claim 1 wherein at least one of the interdigitated rollers is heated above room temperature.
4. The method according to claim 1 wherein the basis weight of the sheet of loop material after the annealing is less than 40 g/m 2 .
5. The method according to claim 4 wherein the basis weight of the sheet of loop material after the annealing is less than 35 g/m 2 .
6. The method according to claim 1 wherein the thermoplastic backing layer comprises at least 5% by weight of an elastomeric polyolefin.
7. The method according to claim 6 wherein the elastomeric polyolefin is a metallocene elastomer.
8. The method according claim 6 wherein the thermoplastic backing layer comprises elastomeric polyolefin in an amount between 5 and 20% by weight.
9. The method according to claim 6 wherein the basis weight of the sheet of loop material is less than 35 g/m 2 .