Creped nonwoven liner with gradient capillary structure

#This invention relates to permanently creped nonwoven materials having low density, high permeability, improved loft and softness, looping, and out-of-plane fiber orientation and both hydrophobic and hydrophilic surfaces.

#Creped thermoplastic nonwoven materials are known from U.S. Pat. No. 4,810,556, issued to Kobayashi et al. In the disclosed process, a raw nonwoven fabric is coated with a lubricant and then pressed between a drive roll and a plate having a rough sandpaper-like surface. The plate is positioned near the drum and is substantially parallel or tangential to the outer surface of the drum. The raw nonwoven fabric is crinkled in a wavelike fashion in the direction of movement of the fabric by the frictional force caused by the pressing. The resulting creped fabric has wavelike crepes which contribute to softness. However, the creping accomplished by this process is not believed to be permanent. It is believed that the creping accomplished by this process can be removed or reduced significantly by subjecting the nonwoven web to mechanical stretching sufficient to flatten out the wavelike crepes. Also, the creping is naturally reduced over time during use of the fabric.

#The creping of paper is also known in the art. However, paper has traditionally been creped using processes different from those used to crepe thermoplastic nonwoven webs. U.S. Pat. No. 3,879,257, issued to Gentile et al., discloses a process used for producing creped paper. A bonding material, preferably elastomeric, is applied to first and second surfaces of the paper so that it covers from about 15-60% of both paper surfaces and penetrates into about 10-40% of the paper thickness from both surfaces. Then, one side of the paper is adhered to a creping surface, such as a creping drum, using the bonding material to cause the adhesion. Then, the paper is creped from the creping surface using a doctor blade positioned at an angle to the surface. This creping method greatly disrupts the fibers in the unbonded regions of the paper increasing the overall softness, absorbency and bulk of the paper, and finely crepes the bonded areas of the paper to soften them.

#FIG. 1 is a schematic side view of one type of an apparatus for producing a permanently creped nonwoven web of the invention.

#FIG. 2 is a greatly enlarged sectional view photograph of an uncreped nonwoven web.

#FIG. 3 is a greatly enlarged sectional view photograph of a permanently creped nonwoven web of the invention, creped on one side to a 25% crepe level.

#"Permanently creped" refers to a creped nonwoven web having bonded and unbonded areas, in which the bonded areas are permanently bent out-of-plane and the unbonded portions are permanently looped, such that the nonwoven web cannot be returned to its original uncreped state by applying a mechanical stress.

#"Crepe level" is a measure of creping and is calculated according to the following equation: ##EQU1##

#"Bent out-of-plane" refers to a bonding or orientation of portions of the nonwoven web in a direction away from the plane in which the nonwoven web substantially lies before being subjected to the creping process. As used herein, the phrase "bent out-of-plane" generally refers to nonwoven webs having creped portions bent at least about 15 degrees away from the plane of the uncreped nonwoven web, preferably at least about 30 degrees.