The meltblown extruder screw has a screw with three zon […]
The meltblown extruder screw has a screw with three zones, the feed zone, the transition zone and the metering zone. The feed zone is the section of the screw where the polymer feed enters the extruder. The transition zone features a decreasing depth and is responsible for homogenizing the polymer feed, while the metering zone increases pressure to prepare the material for discharge through the meltblown die assembly.
Various screw designs are required to produce the different kinds of extrusion products. For example, a grooved-barrel extruder requires a special screw design. A smooth-bore extruder requires a special screw design to melt polymers with lower viscosity, but still needs the same power to melt. The screw introduces energy into the polymer through viscous dissipation and shearing action. The amount of energy introduced is proportional to the viscosity and consistency of the polymer.
The meltblown process differs from other fiber spinning processes in several ways. First, the polymer needs to be filtered more than in other processes. In addition, hot compressed air needs to be provided. Finally, the angle at which air is inserted has to be carefully controlled along the length of the spin head. This restricts the amount of mass a fiber can produce per square meter of web width.
