Purging compounds | processing
Commonly used across the thermoplastics processing industry, purging compound manufacturers are now turning their attention to the compounding sector. Mark Holmes reports
Purging compounds clean up
Purging compounds are widely used across the thermoplastics processing industry where traditional cleaning methods, such as running through virgin resin or regrind, are giving way to use of specially formulated purging compounds. The prime benefit is maintaining uptime through faster changeovers. However, well designed purging compounds also more effectively remove carbon deposits, avoiding the need to remove and clean screws in sensitive production applications. Purging compound developers continue to develop more effective purging solutions for these mainstream processing applications, but are now also turning their attention to the compounding industry, formulating grades that meet the specific requirements of com- pound and masterbatch production. Key areas presenting challenges to compounders
and masterbatchers today include specialty compounds for automotive applications and masterbatches with unique colorants and additives, according to Eric Procunier, Product Development Manager at purging compound developer Asaclean-Sun Plastech, part of the Asahi Kasei Group. “Vibrant neon colours and flame retardants, for example, are very difficult to purge without using commercial purging compounds. In addition, low temperature bio-resins are gaining popularity. The temperatures that the materials process at are often lower than most current purging com- pounds recommended usage temperatures. Chemical purges can be difficult to activate at low temperatures, whereas glass-filled mechanical grades tend to thrive in these environments.” Purging compounds fall into two main categories, defined by their mode of action. Mechanical purging compounds work through shear force and material viscosity difference. They can be formulated to have an affinity for carbon deposits or particular plastic resins but basically “scrub” the equipment clean - there is no chemical reaction and no need for a “soak time”. Chem- ical purging compounds, on the other hand, are better suited to low pressure applications and are designed to react with the plastic resin or carbon deposits to aid
www.compoundingworld.com
removal. Typically, a soak time of up to 30 minutes is required for effective use. Some systems combine both modes of operation. The latest purging compound developments from
Asaclean-Sun Plastech include Asaclean UF2, PF and PX2. The company describes the UF2 grade as a versatile, high performance purging compound particularly suited for colour and material changes for thermoplastic injection moulding, extrusion blow moulding and blown film extrusion machines. The compound can be purged through a die without removing it and effectively removes gels and contami- nation that is not carbonised. It is claimed to have good compatibility with polyethylene resins. “UF2 is a very successful general use grade that has
a very bright future in blow moulding because it holds the parison, and in blown-film extrusion because it is a
April 2017 | COMPOUNDING WORLD 53
Main image: Extruder
screws can be easier to clean
after pre-treat- ment with a suitable
purging agent
PHOTO: POLYTECHS
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90