Ribbon bicomponent fibers have conventionally been produced when the fiber is expected to be split into a smaller fiber using mechanical force or by hydroentanglement (e.g., see U.S. Pat. No. 6,627,025 to Yu). The inventors have conceived of using a bicomponent ribbon fiber according to the disclosure provided herein to increase the loft of a nonwoven.
Bulk is often a desirable property for a nonwoven as it transmits a perception of softness and comfort. For example, softness and comfort are desirable for nonwovens used as topsheet or backsheet in diapers. Bulk is also an important characteristic that affects how a nonwoven will absorb, distribute and retain fluids. Good examples are the nonwovens used as an acquisition and distribution layer disposed between the topsheet and the absorbent core of a diaper.
The bulk of a nonwoven may be increased with the use crimped fibers in the manufacture of the nonwoven. Traditionally, a nonwoven produced from staple fibers is to use fibers that have been mechanically crimped prior to cutting the fibers to the appropriate length. Such fibers appear to have a zig-zag shape.
The typical approach for continuous filaments used in the production of bulky spunbond is to make round fibers using two polymer components having differential shrinkage coefficient when reheated and, to position those fibers in a side-by-side or eccentric way. The differences in shrinkage will force the filament to be twisted in a helix shape. An example of this approach is described in U.S. Pat. No. 5,622,772 to Stoke et al. This approach is sometimes referred to as self-crimped filaments. While this approach can produce a nonwoven with an appearance of high loft, the bulk is easily lost when the nonwoven is compressed by a weight. This is due to the crimps offering little resistance to compression as a result of their shape.
Therefore there is a need for a self-crimped bicomponent fiber and the spunbond made from such fibers that resist compression, therefore maintaining some of the benefit of the high bulk even when under load.