Nonwoven webs having zoned migration of internal additives

Details Nonwoven webs having zoned migration of internal additives Nonwoven webs having zoned migration of internal additives

1998-07-30

2001-03-20

Morris, Terrel (Department: 1771)

Stock material or miscellaneous articles

Structurally defined web or sheet

Discontinuous or differential coating, impregnation or bond

C428S196000, C442S059000, C442S064000, C442S071000, C442S361000

Reexamination Certificate

active

06203889

ABSTRACT:

FIELD OF THE INVENTION
This invention is directed to nonwoven webs having selective, zoned migration of internal additives to create properties affecting only selected regions of the nonwoven web.
BACKGROUND OF THE INVENTION
Hot air knives have been employed for increasing the integrity of nonwoven webs such as spunbonded filament webs. A hot air knife is useful in bonding the individual polymer filaments together at various locations, so that the web has increased strength and structural integrity. Hot air knives are also used for aligning meltblown fibers during manufacture of meltblown webs, for cutting nonwoven fabrics, for chopping reclaim, and for a variety of other uses.
One use of the hot air knife is to improve the structural integrity of nonwoven webs before passing them through standard inter-filament bonding processes. Through-air bonding (“TAB”) is a process of bonding a nonwoven bicomponent fiber web in which air sufficiently hot to melt one of the polymers in the fibers of the web is forced through the web. The air velocity is between 100 and 500 feet per minute and the dwell time may be as long as 6 seconds. The melting and resolidification of the polymer provides the bonding.
A conventional hot air knife includes a mandrel with a slot that blows a jet of hot air onto the nonwoven web surface. U.S. Pat. No. 4,567,796, issued to Kloehn et al., discloses a hot air knife which follows a programmed path to cut out shapes needed for particular purposes, such as the leg holes in disposable diapers. U.S. Pat. No. 5,707,468, issued to Arnold et al., discloses using a hot air knife to increase the integrity of a spunbond web. U.S. application Ser. No. 08/877,377 to Marmon et al., filed Jun. 17, 1998, discloses a zoned hot air knife assembly used to heat discrete portions of a nonwoven web.
It is also known to use heat to facilitate the uniform migration of internal additives from nonwoven webs. U.S. Pat. Nos. 4,857,251, 4,920,168, 4,923,914, and 5,120,888, all issued to Nohr et al., disclose using heat to facilitate the migration of internal additives to the surfaces of nonwoven webs.
SUMMARY OF THE INVENTION
The present invention is directed to nonwoven webs initially having a substantially homogeneous distribution of internal additives. The internal additives are caused to migrate to the surface only in selected regions or “zones” of the nonwoven web, causing the nonwoven web to have desired or enhanced properties only in the selected zones. The selected migration of internal additives can be in the X, Y and/or Z directions, and can cause the nonwoven web to have differential properties in any direction. The invention also includes a method of making a nonwoven web having differential properties in one or more directions, caused by the selected migration of internal additives.


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Manson, John A. and Sperling, Leslie H.:Polymer Blends and Composites,Plenum Press, New York, ISBN 0-306-30831-2, pp. 273-277 (1976).

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