High loft low density nonwoven webs of crimped filaments and methods of making same
AssigneeKimberly-Clark Worldwide, Inc.
InventorsBraulio A. Polanco, Christopher Dale Fenwick, Darryl Franklin Clark, Bryan David Haynes, Kurtis Lee Brown, Chad Michael Freese
Life of this patent
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Abstract
High loft, low density nonwoven webs are produced by forming substantially continuous, spunbond, crimped, bicomponent fibers of A/B bilateral morphology in an unheated fiber draw unit. The fibers are then heated and cooled in the absence of impeding forces to achieve maximum crimp in the z-direction and produce a web of lofted material. The resultant material is particularly suitable for use as an insulator. Particulates may be added to the webs if desired.
Claims24
A method for producing a high loft, low density nonwoven web, the nonwoven web having x, y and z dimensions, with the x dimension being a machine direction, the y dimension being a cross machine direction and the z dimension being a loft direction, comprising:
- a) forming a group of crimpable, substantially continuous, spunbond, bicomponent fibers of A/B morphology in an unheated FDU and depositing the group of fibers onto a forming wire;
- b) first heating the fibers at a time and a temperature sufficient to induce a relaxation of molecular orientation of at least one component of the fiber wherein at most a small degree of nonfunctional bonding occurs between the fibers;
- c) after said first heating, cooling the group of fibers below a crystallization temperature and thereby inducing the fibers to crimp;
- d) minimizing the forces which tend to impede crimping of the fibers when performing steps b) and c) whereby the fibers are allowed to crimp in the z-direction;
- and
- e) reheating the group of fibers to cause the fibers to bond to each other to form a stable high loft, low density nonwoven web.
A process for making a high loft low density nonwoven web of crimped filaments, the process comprising:
- melting polyethylene polymer in an extruder;
- melting polypropylene polymer in an extruder;
- forming the polyethylene polymer and the polypropylene polymer into substantially continuous bicomponent fibers in a spinning apparatus;
- traversing the bicomponent fibers through an unheated fiber draw unit;
- depositing the bicomponent fibers to form a nonwoven web on a forming wire with the aid of below wire exhaust;
- heating the nonwoven web with air having a temperature of about 110 degrees F. to about 260 degrees F. to relax a molecular orientation of at least one of the polymers wherein the bicomponent fibers are nonfunctionally bonded;
- transferring the nonwoven web to a second wire and cooling to below a crystallization temperature of the polymers and thereby allowing the bicomponent fibers to freely form random crimped filaments, wherein the second wire does not have below wire exhaust;
- setting the nonwoven web by reheating with air having a temperature of about 260 degrees F. to about 450 degrees F.
Dependencies are inferred from the claim text.