INNOVATION | ODOUR REDUCTION
Right: One of Evonik’s solutions for odour problems in plastics is called Tego Sorb
the malodour, she adds. Just as important can be degradation of ink resins. Evonik has developed a portfolio of additives that can be used for de-ink- ing, demetallising and delabelling, under the brand Tego Cycle. An odour-reducing additive from Byk, Byk-Max
Below: Odour- absorbing masterbatches enable post- consumer recycled material to be used in applications where smell is critical
P 4200, works similarly to a stripping agent. Its molecular structure is designed so that during compounding it is active on the surface of the polymer in the melt. “This way, the VOCs are almost completely separated from the granulate,” says Jörg Garlinsky, Byk’s Head of Global Thermoplas- tics Industrial Applications. The resulting mixture of VOCs and additive carrier substance is removed during compounding by degassing. Garlinsky says the disadvantage of many adsor- bents currently used for adsorbing VOCs and odours in plastics intended for applications like car interiors, including activated carbon or zeolites (aluminosilicates), is that the VOCs are physically bound to the surface of the adsorbents. “These volatiles may be freed during warm days when the internal temperature of a car exceeds 70°C,” he says. “While adsorbents may delay the release of bound substances, they cannot prevent it entirely. Addition- ally, adsorbents may have an adverse effect on the mechanical properties of a compound.” Stripping agents, such as water, nitrogen or carbon dioxide are added directly into the melt during extrusion, with undesirables being pulled off, preferably using a vacuum. “The downside of this method is the more complex engineering and additional investments required for the associated machinery,” he says. Byk-Max P 4200 is a granulate with a PP carrier. It can be added during extrusion like a regular masterbatch, through the main or side feeder. It works in two steps: first, the active substance is released into the melt by shear force and heat, with pressure build-up during processing preventing
premature expansion of the stripping additive. The stripping additive then evaporates in the vacuum degassing zone, causing increased foaming of the polymer melt. Garlinsky says: “The gas bubbles have a large inner surface area. This process is intensified by the surfactant additive contained in the aqueous active substance of the stripping agent. The stripping agent reduces the solubility of the volatile constituents, which are then extracted during degassing. It has been shown to function for both unfilled and talc-filled compounds.” HPF The Mineral Engineers has also devel- oped novel additives to reduce odours. In tests, its mineral-based odour absorbers were blended into a post-consumer PP recyclate at a level of 5% by weight in a twin-screw extruder. The resulting product was subjected to olfactometric testing according to the VDA 270 standard. The results show that the addition of the newly developed high-performance fillers reduces the odour intensity of the recyclate significantly below the threshold value of 3 and is thus no longer per- ceived as annoying. Masterbatch major Ampacet has extended its
OdorClear range of innovative odour-absorbing masterbatches designed to optimise the use of post-consumer recycled material. Originally introduced as Odor Scavenger, the newly-expand- ed range of powerful wide-spectrum masterbatch- es minimises odours of post-consumer recycled materials and keeps them enclosed inside the polymer, which allows converters to boost packag- ing recycled content. OdorClear masterbatches are designed for use with a broad range of recycled polymers and can
16 PLASTICS RECYCLING WORLD | October 2022
www.plasticsrecyclingworld.com
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IMAGE: AMPACET
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