Sealing/Shutdowns/Startups Contamination Prevention
Most thermoplastic resins when left in the barrel, even for a short time, are likely to degrade and become a cause of product contamination. To prevent contamination or deposit formation use ASACLEAN to clean the barrel and screw and displace resins from the machine.
Shutdown & Sealing:
- Follow the basic ASACLEAN purging instructions to clean the barrel and screw with ASACLEAN purging compound before a temporary or extended shutdown. For grade selection, refer to the ASACLEAN Product Line sheet or speak with a Technical Sales Representative. A filled grade of ASACLEAN, such as EX Grade, cannot be used for sealing the machine.
- When using a filled grade of ASACLEAN for purging the barrel and screw, follow the filled grade with 1/2 barrel capacity of the unfilled sealing grade to displace the filled grade of ASACLEAN.
- Feed one barrel capacity of the unfilled grade of ASACLEAN into the machine with the screw rotation at a slow to medium speed. For molding machines, the screw should be kept in the forward position. As soon as material comes from the machine, stop the screw rotation. To ensure that the barrel is full of ASACLEAN, check the feed throat which should still be filled with ASACLEAN.
- Turn off the heaters with the barrel left full of ASACLEAN. If the heaters are to be left on, contact Asaclean Technical Service for temperature recommendations.
Turn on the heaters set to at least the minimum service temperature for the grade of ASACLEAN being used. The barrel temperature must be at the minimum service temperature long enough for the heat to soak all the way to the screw prior to starting screw rotation.
- If the service temperature of the production resin is above 450°F, (230°C), set the heaters to 450°F, (230°C), until the ASACLEAN has completely plasticized. Then, increase the temperature to the processing temperature of the production resin when ready to begin production.
- Feed a small amount of fresh ASACLEAN to force out the previously charged ASACLEAN. Verify the material is free of contamination. ASACLEAN tends to pick-up additional contaminants if they are present during the shut-down.
- If contamination remains, add a sufficient amount of ASACLEAN to remove the contamination following the general purging instructions.
- Follow the general purging instructions, replacing the newly fed ASACLEAN with the next resin.
- Begin production.