Abstract
Nonwovens production is often adversely affected by non-uniformity associated with fiber laydown and web formation. This non-uniformity is in part a result of the complex interactions between the air streams and the spinning process. Currently, the amount of available research in this area has been minimal with few engineering solutions or references to guide equipment designers. The purpose of this paper is to explore and explain the interaction of air streams engaged in the laying down of nonwovens product onto a porous conveyor or laydown belt. This paper concentrates on the space above the laydown table and the interaction of the fiber stream with the surrounding environment. In this paper, the influence of the ambient and conditioned air will be examined from the spinneret to the forming table. It is assumed for the purposes of this paper that the laydown vacuum is sufficient to evacuate 100% of the combined air streams and a cross-flow quench is used.
Why is air management above the forming or laydown table so important? The control of the air that is feeding the system affects the entire forming area and has a direct impact on web formation and energy cost. The size and complexity of air removal systems are also directly affected by the quantity of entrained air expected in the laydown process. By understanding the process and applying better management techniques, the design, equipment and operational cost for the laydown area can be reduced and also ensure acceptable web formation.
Does entrainment of ambient air affect the formation of the nonwovens web? The formation of the web is directly affected by the amount and aspect of the entrained air available to the system. The interaction between the air laid stream and the surrounding air can cause disruptive eddies within the laydown profile of the nonwoven fiber.
Can the entrained air streams be controlled effectively? By actively supplying the entrained air along the thread path of the fibers and using control devices, such as dampers or valves, adequate control of the entrained air can be attained.