Product/color Changeover
Vol.21 #1, June 1994
When changing products and/or colors in an extrusion process, first bring the temperature up 50 degrees above normal processing levels, introduce a clear polyethylene or polypropylene material of 1.0 to 2.0 MI and purge for a few minutes, then add a few pounds of commercially available chemical purging agent.
Finally, introduce a few minutes more of the clear polyethylene or polypropylene material, follow with the new material and adjust melt temperature to appropriate levels.
The above works both with and without gear pumps.
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