Twin screw color change
Vol. 17 #2, July 1990
Cleaning time between color changes can be sped up, without time consuming screw pulling, when soap water is sprayed into the reed hopper together with the purge resin. Dry color pigments coat the screw flights in the solid conveying section. Soap water wets the pigments, foam and steam will be generated in the barrel which will remove the loose pigments.
After melting is accomplished, the hydraulic wiping in the intermeshing extruder screws will take care of the final clean out. The clean out process is finished, when the soapy foam in the feed opening turns colorless.
See also
Color changes
Twin screw changes