ADDITIVES | RECYCLING
Right: Film recycling is a target market for BASF’s IrgaCycle additive solutions
Finnegan says that higher-performing additives may be needed to ensure successful recyclability of virgin resins, as well as to solve problems in recycled resin. “Incompatible polymers, residues, and contaminants can all find their way into the recycled resin. In addition to preventing the oxidative damage, additive packages must also address challenges with compatibilisation, neutrali- sation of contaminants, and mitigation of problems from residues,” he explains. BASF’s IrgaCycle additive formulations, part of the company’s Valeras portfolio for sustainability, are one-pack solutions designed to be added during regranulation or at the converting step. The products are formulated for specific end markets, such as rigid packaging, flexible packaging, agricultural film, outdoor furniture, and automotive. The company says that the IrgaCycle formulas allow accurate dosing and are more efficient at lower concentrations compared to traditional antioxidant systems. “Traditional antioxidant systems are effective at
addressing damage caused by the oxidation of the polymer. However, in recycled resin, there can be contaminants that accelerate the oxidative damage to the polymer, or that allow for degradation pathways that the antioxidants can’t address directly,” says Finnegan. “The IrgaCycle products contain additional components to address issues specific to recycling and to take the ‘burden’ of the antioxidants. This allows for more efficient use of the antioxidant and can allow for lower loadings of stabilisation.” For example, IrgaCycle PS 031 G has been
formulated to improve the processing of film grade rLDPE. In a multi-pass single-screw extruder experiment, the melt flow rate (MFR) of the rLDPE without restabilisation dropped, indicating cross- linking degradation, while the MFR of rLDPE with IrgaCycle stayed relatively constant or increased
slightly (see Figure 1). The additive also helps main- tain tensile properties, according to BASF.
Figure 1: Melt flow rate (MFR) measured after 1, 3, and 5 extrusion cycles in a single-screw extruder at 220°C showing the effect of BASF’s IrgaCycle PS 031 G stabiliser for rLDPE Source: BASF
50 COMPOUNDING WORLD | October 2022
Sustainable gains Additives are so important when working with PCR because poor quality can be detrimental to processability, part quality, and possibly even carbon footprint. “In many cases, with lower quality PCR, the weight of a part increases and/or the material’s processability is reduced, which poten- tially increases energy use and resulting green- house gas emissions,” says Robert Sherman, Technical Director at Baerlocher. Sherman says that laboratory studies conducted by Baerlocher to mimic real-world conditions confirm that PCR typically needs two to three times more stabilisation than virgin material. “The quality of the incoming content from the materials recovery facility, the stream source, and the washing and sorting processes all play a huge role in determining the amount of stabiliser that’s needed to produce high quality PCR. Our findings show that 2,500 to 4,000 ppm is typically needed,” he says. The company’s Baeropol T-blends were launched a few years ago with several options available for PE and PP. Sherman says T-Blend 1111 TX has emerged as the “workhorse” for many applications. “Baerlocher’s advanced stabilisation additives enable the use of tighter filters under more demanding processing conditions during melt filtration. As a result, fewer gels and impurities are left in the polymer and damage to the polymer architecture is minimised. In the end, the final PCR with our stabilisation additives processes much better and produces a far better final part,” he says. Polymers subjected to multiple heat histories and containing contaminants such as inks, slips,
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