ADDITIVES | RECYCLING
Below: One of the biggest challenges for recyclers is obtaining
consistent and clean material
China’s National Sword policy, enacted in July this
year, has significantly disrupted the recycling market, according to Salvatore J Monte, President of Kenrich Petrochemicals. “The immediate termina- tion of the daily movement of 4,000 shipping containers full of recyclables leaving US ports for China is simply a phenomenon that would mess up any free market segment of the economy,” he says. “The many socio-economic and political facets of
recycling limit the current opportunities for addi- tives for Post-Consumer Recycle (PCR). Collecting, sorting, cleaning and developing market applica- tions for PCR is just too costly for a government mandate or financial supplementation by compa- nies. However, there are applications to be explored in the post-industrial recycle segment because the economics work. For example, at the recent Plastics Industry Association REFOCUS Sustainability & Recycling Summit, a session was devoted to additives for upcycling and a focus was put on upcycling automotive bumpers,” says Monte. “Modern bumpers are made with thermoplastic
olefins, polycarbonates, polyesters, polypropylene, polyurethanes, polyamides, glass fibres, fillers, pigments, coatings and additives of all types. Many of these materials are intrinsically incompatible with each other. Recyclers will tell you that more than 5% PP in HDPE recycle will cause delamination issues for an injection moulder – or that small amounts of fillers will have a significant negative effect on the mechanical properties of a recycled part,” he says. “However, assuming you have a recycle source of reasonable quantity and cost and a market, the challenge becomes processing and compatibility of all of the dissimilar materials.” Monte explains that compatibility can be broken down into the polymer/polymer and filler/fibre/ polymer interfaces. Polymer/polymer interface compatibilisers fall into three general categories: thermoplastic copolymers that tie two dissimilar polymers together; maleated polymers that ‘couple’ two dissimilar polymers; and organometal- lics that catalyse dissimilar polymers of all types and couple fillers in the melt. “Polymers generally
60 COMPOUNDING WORLD | September 2018
fall into two categories depending on the mono- mers and the catalyst(s) used to polymerise - addi- tion polymers and condensation polymers. The limitations of the technologies are that thermoplas- tic copolymers are specific to known streams of recycle, maleated polymer often depolymerise condensation polymers, and organometallic catalysts are expensive and require melt process- ing experience,” he says. Compatibilisation of filler/fibre/polymer inter-
faces, meanwhile, requires coupling agents, such as silanes, titanates, zirconates, aluminates and zirco-aluminates and calls for an understanding - or at least an awareness – of the technologies to take advantage of the possible benefits, according to Monte. “It is important to know these technologies because the more you compatibilise the less you have to clean and sort allowing for more favourable economics in producing a functional recycled plastic part,” he says.
New chemistries Monte says that additive technology requires chemicals and a truly ‘new’ additive requires new chemistry, with the associated inventory registration requirements and outside laboratory toxicological testing. “Ask anybody struggling with the costs of EU REACH registration,” he says. “However, materi- als can always be formulated and called ‘new’.” Kenrich Petrochemicals’ solutions are based on the discoveries of Natta, Ziegler and Kaminsky. “German Karl Ziegler discovered the first titanium- based catalysts and Italian Giulio Natta proposed using them to prepare stereo regular polymers from propylene, and they were awarded the Nobel Prize in Chemistry in 1963,” says Monte. “Ziegler showed that a combination of TiCl4
and Al(C2 with Al(C2 H5 )3 H5 )2 Cl gave
comparable activities for the production of polyeth- ylene. Natta used crystalline α-TiCl3
in combination to produce the first isotactic polypro-
pylene. Kaminsky discovered that titanocene and related complexes emulated some aspects of these Ziegler-Natta catalysts but with low activity. He subsequently found that high activity could be
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PHOTO: SHUTTERSTOCK
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