ADDITIVES | NUCLEATORS AND CLARIFIERS
Above: Brand owners using Milliken’s Millad NX 8000 ECO clarifier can promote its environmental benefits with UL-validated labels
at Blacksburg in North Carolina in the US that will expand its capacity for Millad NX 8000 clarifier by 50%. It is expected to start up this year.
Improving recycling Improving the recycling stream for PP — collection and reuse — is important to meet sustainability targets. In the US, PET post-consumer recycling is well-established but PP has limitations. The coun- try’s Polypropylene Recycling Coalition (of which Milliken is a member) is working to raise $35m to install sorting equipment for recovering PP packag- ing from the post-consumer recycling stream. “Currently, many [US] material recovery facilities (MRFs) only have sorting stations for #1 PET and #2 HDPE bottles. This is one reason why only about 1% of the 170 billion pounds [77 tonnes] of PP consumed last year was recycled, according to the American Chemistry Council. Our goal is to ensure more recyclers can effectively sort waste PP in their facilities,” Adams says. Also aiming to improve recycling, Adeka last
Right: Beta- nucleation can give clear PP cups a solid white appear- ance, poten- tially eliminat- ing the need for TiO2 while improving performance
year introduced its ADK CycloAid brand, which includes one-pack additives for use with recycled resins. ADK CycloAid UPR-011 is a combination of stabiliser and nucleating agent and is intended for use with recycled polyolefins, including recycled PP. The nucleating agent is designed to improve mechanical properties, which can allow increased levels of recycled resin to be used (Figure 2). “At 70% recycled content, you can get to virgin-like quality with 4,000ppm of UPR-011,” says Gupta. “In recycled resins that we evaluated, the secondary antioxidant was consumed and there were more metal impurities. The one-pack can ‘top up’ the formula to make up for this.”
Beta nucleation Beta nucleating agents function differently from other nucleating additives, changing the crystal structure and inducing crystallisation of the beta crystal phase in a film or sheet, which when stretched (such as in a thermoforming or BOPP
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production process) transform into alpha crystals. This solid-state transformation creates voids, which scatter light and make the part appear white, explains Dr Philip Jacoby, independent consultant and President of Jacoby Polymer Consulting. Jacoby helped commercialise beta nucleating agents and, while working for Mayzo, developed a beta nucleating masterbatch. This masterbatch can be used in thermoformed PP to reduce or elimi- nate titanium dioxide, as the additive creates a white part without pigment (recycled resin without pigment has a higher value). An even more significant sustainability driver than
replacing titanium dioxide, however, is the ability to improve light-weighting, according to Jacoby. “In thermoforming, rigidity depends on the process con- ditions and how the material draws into the mould. The beta crystals create a more uniform material distribution throughout a part, such as a drinking cup, which makes the part more rigid overall,” he says. With this increased stiffness, the part can be downgauged without sacrificing functionality and a quality feel. “Reducing the amount of resin used is both an environmental benefit and a cost savings.”
Blown film PP Constab Polyolefin Additives, a member of the Kafrit Group, worked with BASF to develop a clarifying and nucleating additive technology that allows production of blown PP film on standard PE lines. PP blown film production would normally require extrusion lines designed and dedicated for the polymer, according to Michael Weber, Techni- cal Service and R&D manager at Constab. “Although for decades work has been done [by
resin producers] in the PP industry to optimise crystallisation of PP in film and injection moulding, we decided to investigate the potential to make
IMAGE: MILLIKEN
IMAGE: MAYZO/JACOBY CONSULTING
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