Method for manufacturing thermoplastic nonwoven webs and laminates

1. A method of making a nonwoven web of polymer filaments on a collector traveling in a machine direction parallel to a length of the nonwoven web, comprising:

forming a curtain of polymer filaments;

mixing the curtain of polymer filaments with a flow of process air;

depositing the curtain of polymer filaments on the collector to form the nonwoven web;

exhausting the process air through an air intake opening positioned below the collector;

providing a substantially uniform air flow velocity across the air intake opening in a cross-machine direction perpendicular to the machine direction; and

setting an air flow velocity across the air intake opening in the machine direction to thereby define a ratio of the air flow velocity in the machine direction to the air flow velocity in the cross-machine direction.

2. The method of claim 1 wherein setting the air flow velocity across the air intake opening in the machine direction further comprises:

adjusting the air flow velocity in the machine direction so that the polymer filaments in the nonwoven web have a ratio of alignment in the machine direction relative to the cross-machine direction perpendicular.

3. The method of claim 2 wherein the ratio ranges from about 5:1 to about 1:1.

4. The method of claim 1 wherein setting the air flow velocity across the air intake opening in the machine direction further comprises:

regulating the air flow velocity in the machine direction at the air intake opening by adjusting at least one spill air control valve positioned between the air intake opening and a negative pressure source providing the air flow velocity.

5. The method of claim 1 further comprising:

guiding the mixture of the polymer filaments and the process air before depositing the polymer filaments on the collector.

6. The method of claim 5 wherein guiding the mixture of the polymer filaments and the process air further includes:

defining an upstream boundary of the polymer filaments on the collector with a first air directing member upstream from the air intake opening; and

defining a downstream boundary of the polymer filaments on the collector with a second air directing member downstream from the air intake opening.

7. The method of claim 1 wherein the air intake opening includes a forming zone, an upstream zone upstream from the forming zone in the machine direction, and a downstream zone downstream from the forming zone in the machine direction, and exhausting the process air further comprises:

applying a first negative pressure to the forming zone;

applying a second negative pressure to the upstream zone; and

applying a third negative pressure to the downstream zone.

8. The method of claim 7 further comprising:

varying at least one of the second negative pressure and the third negative pressure to change the air flow velocity in the machine direction.

9. The method of claim 7 further comprising:

sensing values for the second and third negative pressures; and

controlling the second and third negative pressures according to the values sensed.

10. The method of claim 9 wherein controlling the second and third negative pressures further comprises:

changing the relative positions of adjustable flow control devices between the air intake opening and a negative pressure source providing the air flow velocity.

11. The method of claim 1 further comprising:

substantially enclosing the air intake opening with a forming chamber.

12. The method of claim 11 further comprising:

regulating the flow of secondary air into the forming chamber from the ambient environment surrounding the forming chamber.

13. The method of claim 1 wherein providing the substantially uniform air flow velocity across the air intake opening in the cross-machine direction further comprises:

controlling the air flow velocity in the cross-machine direction to provide a uniformity in the cross-machine direction of less than about 5.0%.

14. The method of claim 1 wherein mixing the polymer filaments with the flow of process air further comprises:

attenuating the polymer filaments with a flow of process air oriented in the direction of motion of the curtain of polymer filaments toward the collector.

15. The method of claim 1 wherein forming the curtain of polymer filaments further comprises:

extruding the curtain of polymer filaments from a melt spinning assembly positioned above the collector.