Influence of Die Designs on the Produced Nonwoven Webs in Melt Blowing Process

Melt blowing is a process in which polymer melt is extruded through a row of orifices while hot air jets simultaneously attenuate the extrudates and form microfibers. These microfibers lay down randomly on a collector and are subsequently collected as a nonwoven web. Industrial melt blowing processes typically use a traditional die design that dates to the 1950s, comprising a single row of polymer orifices and two narrow slots for air on each side. The conventional designs generate a typical orifice density in the range of 20 to 40 holes per linear inch.  The present work centers on two novel die designs with two-dimensional (non-linear) orifice arrangements, leading to higher orifice density and potentially improved productivity. As a consequence of the two-dimensional nature of these new designs, the fiber spinning aerodynamics is quite different from conventional processes and high-speed visualization was employed to observe the fiber-air jet interaction.  It was found that the near-field interactions of the fiber with the air were dramatically different from conventional one dimensional die system. In addition, it was found that the two-dimensional designs can be used to create helical fibers, with diameter similar to meltblown fibers (1-5 micron), directly from the melt.