Patent ID: 7972985

Claim:
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.