| DPE® 6611 is a fractional melt index low density polyethylene resin that contains various additives to assist in purging and cleaning the extruder. This polymer is formulated with agents to help it wet and scour metal surfaces within the extrusion system. It also contains a blowing agent which helps to disrupt normal flow patterns and enhance scouring action. The resin normally will foam, snap, and crackle as it leaves the die. A somewhat fishy, ammonia smell is detectable from the extrudate and feed hopper. When extruded, the resin has a grayish brown color and a very high viscosity at the die exit. Applications: DPE® 6611 is not required for normal transitions into and out of Surlyn® ionomer resins, Nucrel® acid copolymer resins, and other common polyolefins. The Disco Purge Procedure* is recommended for use during these normal transitions, and special purging compounds such as DPE® 6611 are not part of this procedure. There are instances, however, when it is practical to use a special purging compound like DPE® 6611. Examples include: Cleaning particularly dirty extruders. Removing die lines caused by oxidized polymer deposits. Purging extruders that have chronic purging problems (gels) following runs of Surlyn® resins, Nucrel® resins, Elvax® ethylene vinyl acetate resins, or other specialty resins. Consulting your technical representative is also highly recommended for these cases. Purging prior to extrusion jobs that are particularly sensitive to gels. Facilitating purging for shutdowns when normal Disco Purging has not proven effective. A shutdown is any period of time when the extruder will be completely turned off, such as a weekend or maintenance outage. It is very important that specialty copolymers such as Surlyn® and Nucrel® be completely purged before such a shutdown, as the cool-down, heat-up, and soak periods allow plenty of time to cause significant gel problems. Facilitating rapid removal of pigments from the extruder. DPE® 6611 has also been used to facilitate pulling and cleaning large diameter extrusion screws. However, acrylic purge material is normally used for this purpose. The high viscosity of DPE® 6611 lends itself to easy cleaning of hardware during disassembly, because it peels rather than smearing along the metal surfaces. Although most frequently used on flat die extrusion equipment, DPE® 6611 can also be used for round die converting equipment as well. It can be difficult to purge DPE® 6611 out of standard spiral-fed blown film dies, unless a very low melt index polyethylene is available for this purpose (0.5 MI LDPE or 1.0 MI LLDPE). To activate the blowing agent, the resin must be extruded above about 221°C (430°F). Purging efficiency may be somewhat reduced if the resin does not foam. Information provided by DuPont Packaging Polymers. |
