MACHINERY | RECYCLING & GRANULATORS


Above: Nagoya University researchers have used a ruthenium- based catalyst to break


polymer chains at reduced temperatures and pressures


Breaking bonds Scientists at Nagoya University in Japan have developed a catalyst that can break down polymer chains, which could ease the job of plastics recycling in future. The researchers took a hint from nature – focus- ing on the strong amide bonds that are present in proteins, as well as in synthetic structures like pharmaceuticals and plastics. Breaking amine bonds usually involves large amounts of energy and harsh conditions, said the researchers – whose aim was to achieve this more efficiently. They have done this by developing new ruthenium-based catalysts. “Our previous catalysts could hydrogenate most amide bonds, but the reactions took a long time at high temperature and pressure,” said lead author Takashi Miura. “The new ruthenium catalyst can hydrogenate difficult substrates under much milder conditions.” The earlier catalyst required pressures up to


8MPa and temperatures up to 180˚C, for reaction times of 24-216 hours. The new catalyst can cleave the amide bonds under much gentler conditions (2MPa, and up to 120˚C). Susumu Saito, who leads the research, said: “The


catalyst changes allowed some tricky amide bonds to be selectively cleaved for the first time. It could be used to recover materials from waste plastics to help realise an anthropogenic [human-caused] chemical carbon cycle.” The research was published in Nature Scientific


Reports last year.


Flame retardant recycling At AMI’s Plastics Recycling Technology conference last year, Elke Metzsch-Zilligen, senior scientist at Fraunhofer Institute for Structural Durability and System Reliability (LBF), explained the details of a


26 PIPE & PROFILE EXTRUSION | April 2018


project to understand how plastics containing halogen-free flame retardants (HFFRs) can best be recycled – and whether the process can be im- proved by tailored additivation. “We want to know if closed loop recycling of HFFR polymer compounds is possible,” she said. One aim of the project is to provide a technical demonstration of the recyclability of various HFFR-containing polymers that are commonly used. A second is to communicate the findings to policymakers. The process begins with oven-ageing of polymers, followed by processing by various methods – including injection moulding and film extrusion. The aim is to go through multiple extrusions before the final part is made and tested – as it gives a better dispersion of the flame retardant, even though it may change its chemical structure. One of the methods chosen is to prepare PP film using BASF’s Flamestab NOR 116 FF flame retardant.


Finding contaminants Rami Margalit, recycled materials manager at drip irrigation pipe producer Netafim, told delegates that it has developed a test method to determine solid contaminants in recycled PE – which is commonly used to make the products. “Our production process takes place at very high speed, and can only tolerate very clean and uniform recycled PE,” he said. One problem when using recycled material was having holes in the pipe wall, which is typically caused by a solid contaminant in the melt stream. For this reason, it knew it had to determine the number and size of contaminant particles. The company devised a simple test: pass the


material through a lab extruder – equipped with a filter screen – and examine the residue under a microscope. “As simple as this method was, we were sur- prised to find that the recyclers were not using it,” he said. Contaminants included those from recycled agricultural film – such as sand and wood particles – and from post-industrial waste, such as paper and aluminium foil.


CLICK ON THE LINKS FOR MORE INFORMATION: � www.hellweg-granulators.com � www.neue-herbold.com � www.rapidgranulator.com � http://en.nagoya-u.ac.jp � www.lbf.fraunhofer.de � www.netafim.com


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