Performance and Benefits of Side-Fed Die Technology for Blown Film Applications, 2000 Polymers, Laminations & Coatings Conference Proceedings

Ricky Keller--By applying new technology to an old, little-used concept for blown film die design, a new series of side-fed dies promises some advantages to film processors. Typical blown film dies are fed polymers from the bottom of the die where radial feed tubes distribute the melted polymer to the start of the spiral section. The spiral section then distributes the polymer evenly around the die. Due to the nature of the radial feedtubes, space inside the die is limited for internal bubble cooling passages. Additionally, the wetted surface area can become quite large on coextrusion dies utilizing this design.

The side-fed concept to be discussed uses a “coat-hanger” style, single channel that decreases in volume to uniformly feed the bottom of a spiral distribution section. The combination of this single channel and the spiral section creates a versatile die design that offers several advantages. These advantages include a decreased wetted surface area, radically lower residence times, and increased space for internal air delivery systems, especially on small diameter dies. A conical, stackable mandrel makes it possible to build coextrusion dies of excellent purgeability.