processing | Purging compounds
changeovers for most commodity and engineering grade resins processed up to 345°C. Its foaming action makes it particularly suitable for applications involving low flow or low pressure environments. Another grade, NCT, is formulated for applications
involving higher processing temperatures; it also has a foaming action. “This grade can be used for sealing during machine shutdowns to prevent carbon develop- ment and facilitate start-ups,” says marketing manager Miyuki Matsumine. Several months ago, Sun Plastech also introduced
Above: Using the correct purge com- pound for screw pulls can significantly accelerate the process as the compounds are formulated for easy release from the surface of the screw and barrel
eliminating black specks caused by thermal degrada- tion. The company says that, compared to conventional cleaning processes and products, the use of Lusin Clean 1010 can lead to reductions in total costs due to material consumption, down times and scrap rates of 30 to 70%. RapidPurge has been on the market with a range of
purging compounds for over 35 years and says it has products that defeat the most demanding hostile thermoplastic processing challenges, including carbon build-up and difficult colour changeovers. The company currently offers more than 25 different grades, includ- ing chemical, mechanical, chemical/mechanical formulations, and custom blends. They are available in pelletized or powder form, as ready-to-use pre-mixes or cost-effective concentrates. “We have many compounders using our chemical and/or mechanical products because RapidPurge saves them from pulling screws when switching over to their next material or colour. In the situations where they have to pull screws, using RapidPurge before teardown makes the job much easier,” says Mary Kinney in sales and marketing at the company. “The selection criteria are based largely on operating temperature, viscosity and preference for pre-mix versus concentrated. Our products are available with different PE base resins to match temperature and viscosity requirements.” Asaclean is another well-known mechanical purging
Right: If using a strand die it is important to choose a purging
compound that will flow to the outer boundaries,
recommends Shuman Plastics
56
compound. It has been supplied by Asahi Kasei Chemicals in Japan for 25 years, as well as by various subsidiaries around the world. Sun Plastech looks after the Americas, and has local production. Last June, it acquired rival Novachem and now sells its ex-Nova- chem purging products as the Asaclean N-Series. These include chemical, mechanical, and hybrid types. N-Series products feature chemical purging grades
that are suitable for the low flow or low pressure environments typical in extrusion applications including compounding, profile, extrusion and blow moulding. The range includes NCR, described as a versatile, general purpose grade especially suited for colour and material
COMPOUNDING WORLD | January 2016
www.compoundingworld.com
new high temperature grades, Asaclean PF and PX2, specifically formulated for resins such as PPS, PEI, PEEK, and LCP that have high processing temperatures. Asaclean PF is suitable for colour and material changeo- vers and can also be used as a sealing material during machine shutdowns within a temperature range of 280-420°C. PXS, which is glass-filled, works on hard-to-clean resins and carbon removal at up to 420°C. Eric Procunier, Product Development Manager at Sun
Plastech, highlights how purging compounding lines differs from other types of extrusion lines. “A typical compounding line will have multiple ports where additives are introduced to the melt. These ports are areas of low melt pressure, and are often difficult for purging compounds to clean,” he says. “Because of these differences and challenges, compounding is an area that is currently under-served by commercial purging compounds. However, we have been seen an increasing number of compounders are giving it a try and taking advantage of improved efficiencies and cost savings. “Contamination in a continuous process like extru-
sion can cause long hours of down time. Once contami- nation begins, it is almost impossible to stop without aggressive intervention – either a screw pull and clean manually, or use of a purging compound. There is nothing worse than extended unplanned downtime due to a screw pull. But the best way to combat contamina- tion is not to make it in the first place.” Matsumine confirms that compounders are reluctant
PHOTO: SHUMAN PLASTICS
PHOTO: SHUMAN PLASTICS
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