Nonwoven fabric and process of producing the same
A nonwoven fabric 10 has a first layer 1 containing crimped fibers 11 . In the layer 1 , the crimped fibers gather in parts to form a large number of fiber clusters 12 that are distributed all over the layer 1 . The clusters 12 interconnect to each other to form a network structure in the layer 1 . The nonwoven fabric 10 further has another fiber layer as a second layer 2 disposed on a side of the first layer 1 . The two layers are partly joined at a large number of joints 3 . The second layer 2 protrudes outwardly between the joints 3 to form a large number of protrusions 20.
1. A nonwoven fabric comprising a first layer containing self-crimping fibers and a second layer containing heat fusible fibers, wherein the self-crimping fibers gather in parts of the first layer to form a large number of fiber clusters, the clusters being distributed all over the first layer in a staggered pattern and each cluster has a length of 200 to 5,000 μm and a width of 30 to 100 μm in a plan view,
wherein the clusters interconnect with each other to form a network structure in the first layer,
wherein the nonwoven fabric is produced by forming the first layer by opening the self-crimping fibers on a card to form a carded web, superposing the first layer and the second layer, heat-embossing the first layer and second layer to produce a composite web, and heat-treating the composite web thereby shrinking the first layer and forming protrusions in the second layer,
wherein the heat-treating is performed in a heat shrinking unit at a temperature ranging from a temperature at which the self-crimping fibers start shrinking to 110° C. for 2 to 10 seconds while transferring the composite web into the heat shrinking unit at an overfeed of 50% to 80% in the machine direction and controlling the shrinkage of the composite web in the heat shrinking unit such that the width of the composite web in the direction perpendicular to the machine direction of the composite web reduces to 50% to 90% of that before shrinkage, and
wherein the self-crimping fibers comprise a polypropylene core and a polyethylene sheath and the self-crimping fibers are coil-shaped after the composite web is heat-treated and the self-crimping fibers shrink, and each cluster is a gathering of self-crimping fibers entangled with each other in an oblong geometry.
2. The nonwoven fabric according to claim 1 , wherein the individual clusters are oblong, and the front end of any one of the clusters connects to the rear end of another one of the clusters adjacent to the any one of the clusters in the longitudinal direction of these clusters via a connecting part made of a fewer fibers of the self-crimping fibers than the clusters.
3. The nonwoven fabric according to claim 2 , wherein the clusters are unidirectionally oriented.
4. The nonwoven fabric of claim 1 , wherein the clusters are oriented in the machine direction.
5. The nonwoven fabric of claim 1 , wherein the nonwoven fabric has a double-ply or multi-ply structure comprising at least two layers comprising clusters of self-crimping fibers, and wherein the layers are connected to each other by the self-crimping fibers.
6. A topsheet for an absorbent article comprising the nonwoven fabric of claim 1 , wherein the topsheet is applied to an absorbent member with the first layer facing the absorbent member.