While sustainability is a relatively new term in plastics, rotary batch mixing is an old warhorse in many processing operations. But the two came together in Auburn, Pa., where film processor Omnova Solutions credits mixers from Munson Machinery Co. Inc., Utica, N.Y., for enabling efficient in-house recycling. Omnova compounds, calenders, prints, embosses, and coats primarily PVC films. Over the years Omnova has cut its scrap rate significantly, but the calendering process inherently generates waste material that could be recycled. In an effort to effectively reuse this material and improve the plant’s environmental footprint, Omnova purchased a Munson 700-TSC-300 rotary batch mixer with capacity of 18,000 lb. The company granulates its start-up and process waste material and then blends it in the mixer. One benefit of the machine’s mixing efficiency was to reduce variations in particle-size distribution, says Steve Reed, process engineer. This prevents particle segregation and problems arising from different melt temperatures during reprocessing.
The company was recycling a handful of colors at the time—black, white, and blends of red, green, and blue. The ability of the mixer to produce consistent blends made in-house recycling possible. “The blends that we were releasing to production had to be within a pretty tight color tolerance,” Reed says. The rotary batch mixer achieves homogeneous blending through the use of internal mixing flights that tumble, turn, cut, and fold the batch. The gravity-fed process produces uniformly mixed batches in 3 min or less and achieves full discharge. The mixer has a small footprint, dust-tight operation, and low energy consumption. With more materials and colors added to the production schedule, Omnova invested in a second, smaller Munson mixer with a capacity of 5000 lb.