Process for creating a variable density, high loft, non-woven web structure
A process is disclosed for creating air laid, high loft, non-woven, variable density web structures. The fiber manipulation and distribution necessary to produce a variable weight and density web is accomplished by creating variable, negative pressure regions across the surface of a condenser or other vacuum screen, which causes fibers to migrate toward areas of lower pressure. Also disclosed are embodiments of condenser and vacuum screens for producing such variable density web structures.
1. A process for creating a variable density, high loft, non-woven web structure, the process comprising the steps of:
(a.) establishing a non-uniform vacuum across the surface of a condenser screen in parallel banded regions to produce at least a first area having greater airflow than a second area; and
(b.) condensing fiber onto said condenser screen in a non-uniform variable density arrangement across the surface of said condenser screen;
wherein fiber is directed more heavily to the first area of the condenser screen having greater airflow, and fiber is directed less heavily to the second area of the condenser screen having lesser airflow;
thereby, resulting in a high loft, non-woven web structure having density variations corresponding to the areas along the surface of said condenser screen having greater and lesser airflow.
2. The process of claim 1 wherein said condenser screen is a cylindrical condenser screen.
3. The process of claim 1 wherein said condenser screen is a vacuum screen.
4. The process of claim 1 wherein said condenser screen comprises at least one region having no holes.
5. The process of claim 1 wherein said condenser screen is selected from the group consisting of a static vacuum screen, a rotating vacuum screen, and a vacuum conveyor.
6. The process of claim 1 wherein regions of holes within said condenser screen are blocked, or otherwise obstructed, in spaced-apart, parallel arrangement across the surface of the condenser screen.
7. The process of claim 1 wherein said condenser screen comprises a plurality of regions having no holes.
8. The process of claim 1 wherein said condenser screen comprises at least one region having unbalanced or non-uniform hole patterns or hole distributions.
9. The process of claim 1 wherein said condenser screen comprises at least one region having smaller holes.
10. The process of claim 1 wherein said condenser screen comprises at least one region having a hole pattern or hole distribution varying from at least one other region of said condenser screen.