additives | Recycling
Brabender Plasticorder blends of three recycled polymers – PP, PET and PE. The image on the left shows the incompatibility when no additive is used; the right image shows the same blend compatibilised with 1.5% of Ken-React CAPS KPR 12/LV pellets from Kenrich
Right: The PET bottle on the left contains 25% PCR and shows consid- erable loss of optical quality; the bottle on the right has the same PCR content but uses 0.05% of Clariant’s optical
brightener for PET
Petrochemicals. “Add a third polymer and it really gets complicated. The additive pellet can be used just like a colour concentrate, but must be melt compounded at around 10% lower temperatures than normal to create reactive compounding shear because the catalyst reduces melt viscosity.” Kenrich says the lower processing temperature is required to apply the appropriate work energy at the interface of the dissimilar macro- molecules to optimise the 1.5nm catalyst’s complete reaction. “Conventional discussions on
recycled plastics centre around equipment that sorts, cleans, demagnetises, washes, granulates, bales or melt processes recyclate – or polymer compatibilisers based on maleic anhydride chemistry or bipolar thermoplastics that have affinity for two select recycle polymer streams. Our new KPR (Kenrich Plastic Recycle) catalyst causes multiple polymers of divergent chemistry to repolymerise in the melt to form not alloys, but new complex co-polymers having much higher mechanical properties. It is a new way to look at PCR and achieve high loadings of PCR in virgin polymers to meet sustainability mandates in consumer plastic packaging products, such as blow moulded soap bottles,” says Monte.
Table 1: Spectrophotometer measurements of a PET blend containing 25% PCR resin with various levels of Clariant’s HiFormer PET optical brightener additive
Db (Blue) Test 1 Db (Blue) Test 2 Source: Clariant
44
0% (Control) 1.84 3.15
0.025% 1.69 3.05
% Additive 0.035% 0.97 0.64
0.05% 0.34
-0.71
Optical brightening Deterioration of optical properties is a key problem for those working with reprocessed resins, particularly PET. Clariant has introduced a liquid additive master- batch that minimises yellowing and greying of PET polymers caused by the introduction of post-consumer- recycled resin (PCR). The new optical brightening products, which are part of the firm’s HiFormer range of liquid masterbatch solutions and application technol- ogy, can be used in a wide variety of PET resin grades and processes, including injection-blow moulding, injection moulding and extrusion. The additive has received approval for food-contact applications from the US Food & Drug Administration. “Packagers are under heavy pressure from consum-
ers and environmental advocates to use more PCR in their products,” says Peter Prusak, head of Marketing at Clariant Masterbatches North America. “However, the recyclate tends to reduce or discolour the crystal clarity that PET is known for. Clariant’s new HiFormer PET-enhancing additives promise to minimise this problem, opening new opportunities for more sustainable packaging.” Clariant says that the liquid
masterbatches are resistant to sedimentation and segmentation so they offer extended storage shelf life. They are also easy to use in gravimetric metering systems, ensuring accurate dosing and clean operation. Let-down ratios as low as 0.025% have been used successfully, the company says. Clariant has assessed the
performance of the new liquid additives in tests carried out on a production scale blow moulding machine in its facility in East Chicago, US. Bottles made using 25% recycled PET and 75% virgin PET with no brightening additive were compared against bottles made with the same PCR resin and the new additive at additions of 0.025, 0.035 and 0.05%. While the unmodified bottles showed significant yellowing, all the bottles made with the HiFormer additive were visibly brighter, displaying much less yellow and more blue (Table 1 shows the spectrophotometer readings). Clariant says that the data in the two tests are quite
different due to the fact that the bottles tested were essentially transparent. However, the trend is the same in both Test 1 and Test 2 in that the blue value decreas- es as the concentration of the optical brightener increases. This indicates that less blue light is absorbed by the surface of the PET and more blue light is reflected toward the viewer’s eye. “The human eye
COMPOUNDING WORLD | April 2016
www.compoundingworld.com
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